Fix use of undeclared identifier 'CHECK_NOSPARSE_CONTIGUOUS_CUDA' with USE='-flash'

Bug: https://github.com/pytorch/pytorch/issues/160826
--- a/aten/src/ATen/native/transformers/cuda/attention.cu
+++ b/aten/src/ATen/native/transformers/cuda/attention.cu
@@ -71,6 +71,7 @@
 #include <ATen/native/transformers/cuda/sdp_utils.h>
 #include <ATen/native/transformers/sdp_utils_cpp.h>
 
+#include <ATen/native/transformers/flash_api_common.h>
 #ifdef USE_FLASH_ATTENTION
 // FlashAttention Specific Imports
 #include <ATen/native/transformers/cuda/flash_attn/flash_api.h>
--- a/aten/src/ATen/native/transformers/cuda/attention_backward.cu
+++ b/aten/src/ATen/native/transformers/cuda/attention_backward.cu
@@ -33,6 +33,7 @@
 #include <ATen/ops/_scaled_dot_product_flash_attention_backward_native.h>
 #endif
 
+#include <ATen/native/transformers/flash_api_common.h>
 #ifdef USE_FLASH_ATTENTION
 // FlashAttention Specific Imports
 #include <ATen/native/transformers/cuda/flash_attn/flash_api.h>
--- /dev/null
+++ b/aten/src/ATen/native/transformers/flash_api_common.h
@@ -0,0 +1,28 @@
+#pragma once
+#include <cstdint>
+#include <limits>
+
+#include <ATen/core/Tensor.h>
+#include <c10/util/Exception.h>
+
+#define CHECK_NOSPARSE_CONTIGUOUS_CUDA(TENSOR)                            \
+  TORCH_CHECK(TENSOR.is_cuda(), #TENSOR " must be a CUDA tensor");     \
+  TORCH_CHECK(!TENSOR.is_sparse(), #TENSOR " must be a dense tensor"); \
+  TORCH_CHECK(TENSOR.is_contiguous());
+
+#define CHECK_NOSPARSE_LASTCONTIGUOUS_CUDA(TENSOR)                        \
+  TORCH_CHECK(TENSOR.is_cuda(), #TENSOR " must be a CUDA tensor");     \
+  TORCH_CHECK(!TENSOR.is_sparse(), #TENSOR " must be a dense tensor"); \
+  TORCH_CHECK(                                                         \
+      TENSOR.stride(-1) == 1, #TENSOR ": last dimension must be contiguous");
+
+#define CHECK_ALIGNED_PTR(PTR, ALIGNMENT) \
+  TORCH_CHECK(                         \
+      uint64_t(PTR) % ALIGNMENT == 0, #PTR " is not correctly aligned")
+
+#define ASSIGN_CHECK_OVERFLOW(A, B)                                    \
+  {                                                                    \
+    A = B;                                                             \
+    TORCH_CHECK(                                                    \
+        B < std::numeric_limits<decltype(A)>::max(), #B " overflows"); \
+  }
--- a/aten/src/ATen/native/transformers/hip/flash_attn/flash_api.h
+++ b/aten/src/ATen/native/transformers/hip/flash_attn/flash_api.h
@@ -4,28 +4,7 @@
 #include <ATen/Context.h>
 #include <ATen/core/Tensor.h>
 #include <c10/util/Exception.h>
-
-#define CHECK_NOSPARSE_CONTIGUOUS_CUDA(TENSOR)                            \
-  TORCH_CHECK(TENSOR.is_cuda(), #TENSOR " must be a CUDA tensor");     \
-  TORCH_CHECK(!TENSOR.is_sparse(), #TENSOR " must be a dense tensor"); \
-  TORCH_CHECK(TENSOR.is_contiguous());
-
-#define CHECK_NOSPARSE_LASTCONTIGUOUS_CUDA(TENSOR)                        \
-  TORCH_CHECK(TENSOR.is_cuda(), #TENSOR " must be a CUDA tensor");     \
-  TORCH_CHECK(!TENSOR.is_sparse(), #TENSOR " must be a dense tensor"); \
-  TORCH_CHECK(                                                         \
-      TENSOR.stride(-1) == 1, #TENSOR ": last dimension must be contiguous");
-
-#define CHECK_ALIGNED_PTR(PTR, ALIGNMENT) \
-  TORCH_CHECK(                         \
-      uint64_t(PTR) % ALIGNMENT == 0, #PTR " is not correctly aligned")
-
-#define ASSIGN_CHECK_OVERFLOW(A, B)                                    \
-  {                                                                    \
-    A = B;                                                             \
-    TORCH_CHECK(                                                    \
-        B < std::numeric_limits<decltype(A)>::max(), #B " overflows"); \
-  }
+#include <ATen/native/transformers/flash_api_common.h>
 
 namespace pytorch_flash {