glsl: add process_qualifier_constant() helper
glsl: add process_qualifier_constant() helper

For now this just validates that a qualifier is inside its
minimum boundary, in a later patch we will expand it to
evaluate compile time constants.

Reviewed-by: Samuel Iglesias Gonsálvez <b753b212f30aed827c3eea2e437609dc37310153@igalia.com>
Reviewed-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler