Clamp masked writes to mapped memory region against size. Closes #2268

* When manually masking writes to mapped memory with tiled resources we need to
  avoid overrunning the bounds of the mapped region.

renderdoc/driver/vulkan/wrappers/vk_resource_funcs.cpp

@@ -1103,6 +1103,9 @@ bool WrappedVulkan::Serialise_vkFlushMappedMemoryRanges(SerialiserType &ser, VkD
         // *sooner*.
         size_t size = size_t(RDCMIN(it->finish(), finish) - offs);
 
+        // cap the size by the mapped memory region
+        size = RDCMIN(MemRange.size, size);
+
         memcpy(MappedData + offs, m_MaskedMapData.data() + offs, size);
       }