radeonsi: use proper GRBM_GFX_INDEX offset for CI+
radeonsi: use proper GRBM_GFX_INDEX offset for CI+

The offset is different on CI and newer.

Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>
Signed-off-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler