Add break for default cases

Visual Studio has an option to search all files in a solution, so I
did a search in there for "default:" looking for any missing break
statements.

I've left out default statements that return something, and that throw
something, even if via ThrowInvalidType. UNREACHABLE leads towards throw

R_THROW macro leads towards a return

src/video_core/renderer_opengl/gl_texture_cache.cpp

@@ -891,6 +891,7 @@ void Image::CopyBufferToImage(const VideoCommon::BufferImageCopy& copy, size_t b
         break;
     default:
         ASSERT(false);
+        break;
     }
 }
 
@@ -927,6 +928,7 @@ void Image::CopyImageToBuffer(const VideoCommon::BufferImageCopy& copy, size_t b
         break;
     default:
         ASSERT(false);
+        break;
     }
     // Compressed formats don't have a pixel format or type
     const bool is_compressed = gl_format == GL_NONE;

src/video_core/renderer_opengl/renderer_opengl.cpp

@@ -340,6 +340,7 @@ void RendererOpenGL::ConfigureFramebufferTexture(TextureInfo& texture,
         texture.gl_type = GL_UNSIGNED_INT_8_8_8_8_REV;
         // UNIMPLEMENTED_MSG("Unknown framebuffer pixel format: {}",
         //                   static_cast<u32>(framebuffer.pixel_format));
+        break;
     }
 
     texture.resource.Release();