vk_stream_buffer: Respect non coherent access alignment

* Required by nvidia GPUs on MacOS

src/video_core/renderer_vulkan/vk_instance.h

@@ -205,6 +205,11 @@ public:
         return properties.limits.minUniformBufferOffsetAlignment;
     }
 
+    /// Returns the minimum alignemt required for accessing host-mapped device memory
+    vk::DeviceSize NonCoherentAtomSize() const {
+        return properties.limits.nonCoherentAtomSize;
+    }
+
     /// Returns the maximum supported elements in a texel buffer
     u32 MaxTexelBufferElements() const {
         return properties.limits.maxTexelBufferElements;

src/video_core/renderer_vulkan/vk_stream_buffer.cpp

@@ -94,6 +94,10 @@ StreamBuffer::~StreamBuffer() {
 }
 
 std::tuple<u8*, u64, bool> StreamBuffer::Map(u64 size, u64 alignment) {
+    if (!is_coherent && type == BufferType::Stream) {
+        size = Common::AlignUp(size, instance.NonCoherentAtomSize());
+    }
+
     ASSERT(size <= stream_buffer_size);
     mapped_size = size;
 
@@ -122,6 +126,10 @@ std::tuple<u8*, u64, bool> StreamBuffer::Map(u64 size, u64 alignment) {
 }
 
 void StreamBuffer::Commit(u64 size) {
+    if (!is_coherent && type == BufferType::Stream) {
+        size = Common::AlignUp(size, instance.NonCoherentAtomSize());
+    }
+
     ASSERT_MSG(size <= mapped_size, "Reserved size {} is too small compared to {}", mapped_size,
                size);