Introduce convenience constexpr for memory access types (pytorch#5592)

Summary:
Pull Request resolved: pytorch#5592

Title says it all.

Reviewed By: jorgep31415

Differential Revision: D63327955

fbshipit-source-id: f3203ccea2d6e693b486207f4a5434a809dced3c

Author: SS-JIA

backends/vulkan/runtime/vk_api/memory/Buffer.h

@@ -35,6 +35,13 @@ enum MemoryAccessType : MemoryAccessFlags {
   WRITE = 1u << 1u,
 };
 
+static constexpr MemoryAccessFlags kReadWrite =
+    MemoryAccessType::WRITE | MemoryAccessType::READ;
+
+static constexpr MemoryAccessFlags kRead = MemoryAccessType::READ;
+
+static constexpr MemoryAccessFlags kWrite = MemoryAccessType::WRITE;
+
 class VulkanBuffer final {
  public:
   struct BufferProperties final {