i965: Consolidate some of the intel_blit logic
i965: Consolidate some of the intel_blit logic

An upcoming patch is going to introduce some code here, and having this code
organized as the patch does makes it a bit easier to read later.

There should be no functional change here.

Signed-off-by: Ben Widawsky <73675debcd8a436be48ec22211dcf44fe0df0a64@bwidawsk.net>
Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler