fix metal shader lack of texutre uniform variable
fix metal shader lack of texutre uniform variable

LWJGL-CI/bgfx,MikePopoloski/bgfx,LWJGL-CI/bgfx,mendsley/bgfx,attilaz/bgfx,jdryg/bgfx,fluffyfreak/bgfx,LWJGL-CI/bgfx,emoon/bgfx,bkaradzic/bgfx,fluffyfreak/bgfx,jdryg/bgfx,MikePopoloski/bgfx,MikePopoloski/bgfx,bkaradzic/bgfx,bkaradzic/bgfx,jdryg/bgfx,jpcy/bgfx,attilaz/bgfx,emoon/bgfx,emoon/bgfx,fluffyfreak/bgfx,mendsley/bgfx,mendsley/bgfx,jpcy/bgfx,fluffyfreak/bgfx,jdryg/bgfx,jpcy/bgfx,jpcy/bgfx,LWJGL-CI/bgfx,bkaradzic/bgfx,attilaz/bgfx