svga: fix the test for sRGB texture formats
svga: fix the test for sRGB texture formats

The pipe_sampler_view::format field should be prefered over the resource/
texture format.  The former is used to override the texture format for
sRGB decode enable/disable, etc.

Also, use new util_format_is_srgb() helper to catch all sRGB formats.

This fixes the piglit tex-srgb test for GL_EXT_texture_sRGB_decode.

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