[llvm] [docs][AMDGPU] move DMA operations to a separate file (PR #206917)

[Sameer Sahasrabuddhe via llvm-commits]

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@@ -0,0 +1,145 @@
+(amdgpu-dma-operations)=
+
+# AMDGPU DMA Operations
+
+```{contents}
+:local:
+```
+
+## Introduction
+
+DMA operations transfer data between different kinds of memory directly without
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ssahasra wrote:

Done. 

https://github.com/llvm/llvm-project/pull/206917