mesa: simplify some _mesa_IsEnabled() queries
mesa: simplify some _mesa_IsEnabled() queries

No need to test array->Enabled != 0 since the Enabled field can
only be 0 or 1.

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Reviewed-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@linux.intel.com>

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