radeonsi: add a helper for extracting bitfields from parameters (v2)
radeonsi: add a helper for extracting bitfields from parameters (v2)

This will be used a lot (especially by tessellation).

v2: don't use the bfe intrinsic

Reviewed-by: Tom Stellard <85590917cb30a670bf23f5b4273617f8815d1e87@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler