Fixed uninitialized memory due to missing returns in canary

Functions which are suppose to crash on non canary builds usually don't return anything which lead to uninitialized memory being used.

src/video_core/gpu.cpp

@@ -102,6 +102,7 @@ u32 RenderTargetBytesPerPixel(RenderTargetFormat format) {
         return 1;
     default:
         UNIMPLEMENTED_MSG("Unimplemented render target format {}", static_cast<u32>(format));
+        return 1;
     }
 }
 
@@ -119,6 +120,7 @@ u32 DepthFormatBytesPerPixel(DepthFormat format) {
         return 2;
     default:
         UNIMPLEMENTED_MSG("Unimplemented Depth format {}", static_cast<u32>(format));
+        return 1;
     }
 }