util: Fix PIPE_FORMAT_R8G8B8_SRGB swizzles.
util: Fix PIPE_FORMAT_R8G8B8_SRGB swizzles.

The only user of PIPE_FORMAT_R8G8B8_SRGB is mesa, which
per src/mesa/main/texstore.c interprets it as

  R8 G8 B8

and not the other way around.

bkaradzic/glsl-optimizer,benaadams/glsl-optimizer,jbarczak/glsl-optimizer,metora/MesaGLSLCompiler,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,mapbox/glsl-optimizer,mcanthony/glsl-optimizer,zz85/glsl-optimizer,benaadams/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,wolf96/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,zz85/glsl-optimizer,KTXSoftware/glsl2agal,adobe/glsl2agal,mcanthony/glsl-optimizer,zeux/glsl-optimizer,djreep81/glsl-optimizer,bkaradzic/glsl-optimizer,tokyovigilante/glsl-optimizer,djreep81/glsl-optimizer,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,tokyovigilante/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer,adobe/glsl2agal,dellis1972/glsl-optimizer,zeux/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,benaadams/glsl-optimizer,adobe/glsl2agal,wolf96/glsl-optimizer,mapbox/glsl-optimizer,bkaradzic/glsl-optimizer,KTXSoftware/glsl2agal,dellis1972/glsl-optimizer,wolf96/glsl-optimizer,mapbox/glsl-optimizer,tokyovigilante/glsl-optimizer,benaadams/glsl-optimizer,KTXSoftware/glsl2agal,zeux/glsl-optimizer,wolf96/glsl-optimizer,metora/MesaGLSLCompiler,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,metora/MesaGLSLCompiler,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,adobe/glsl2agal,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,zz85/glsl-optimizer,adobe/glsl2agal,zeux/glsl-optimizer,KTXSoftware/glsl2agal,mcanthony/glsl-optimizer,tokyovigilante/glsl-optimizer