anv/pipeline: Make is_dual_src_blend_factor inline
anv/pipeline: Make is_dual_src_blend_factor inline

It's not used on gen8+ so it causes unused function warnings.

Reviewed-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler