buffer_cache: Return stream buffer invalidation in Map instead of Unmap

We have to invalidate whatever cache is being used before uploading the
data, hence it makes more sense to return this on Map instead of Unmap.

src/video_core/buffer_cache/buffer_cache.h

@@ -110,19 +110,23 @@ public:
         });
     }
 
-    void Map(std::size_t max_size) {
+    /// Prepares the buffer cache for data uploading
+    /// @param max_size Maximum number of bytes that will be uploaded
+    /// @return True when a stream buffer invalidation was required, false otherwise
+    bool Map(std::size_t max_size) {
         std::lock_guard lock{mutex};
 
+        bool invalidated;
         std::tie(buffer_ptr, buffer_offset_base, invalidated) = stream_buffer->Map(max_size, 4);
         buffer_offset = buffer_offset_base;
+
+        return invalidated;
     }
 
-    /// Finishes the upload stream, returns true on bindings invalidation.
-    bool Unmap() {
+    /// Finishes the upload stream
+    void Unmap() {
         std::lock_guard lock{mutex};
-
         stream_buffer->Unmap(buffer_offset - buffer_offset_base);
-        return std::exchange(invalidated, false);
     }
 
     void TickFrame() {
@@ -576,8 +580,6 @@ private:
     std::unique_ptr<StreamBuffer> stream_buffer;
     BufferType stream_buffer_handle{};
 
-    bool invalidated = false;
-
     u8* buffer_ptr = nullptr;
     u64 buffer_offset = 0;
     u64 buffer_offset_base = 0;