gallivm: avoid unnecessary URem in linear wrap repeat case
gallivm: avoid unnecessary URem in linear wrap repeat case

Haven't looked at what code this exactly generates but URem can't be fast.
Instead of using two URem only use one and replace the second one with
select/add (this is what the corresponding aos code already does).

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