gallium/util: Use PIPE_TRANSFER_DISCARD_RANGE in pipe_buffer_write.
gallium/util: Use PIPE_TRANSFER_DISCARD_RANGE in pipe_buffer_write.

Additionally, to discarding the whole buffer, use
PIPE_TRANSFER_DISCARD_RANGE in pipe_buffer_write when the
write covers only part of the buffer.

Signed-off-by: Mathias Fröhlich <f51464c0d83b5283880370f10770eaa83440cc6a@web.de>

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