Fix a latent issue of NGG GS
Fix a latent issue of NGG GS

We should only handle GS message when mutating GS. Other messages from
s_sendmsg should be skipped.

GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc