radeonsi: set some VGT context registers on SI-CI
radeonsi: set some VGT context registers on SI-CI

the kernel sets them, but other UMDs can change them

Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler