i965: Optimize brw_inst_set_bits() and brw_compact_inst_set_bits().
i965: Optimize brw_inst_set_bits() and brw_compact_inst_set_bits().

Cuts about 2k of .text.

   text     data      bss      dec      hex  filename
5017141   197160    27672  5241973   4ffc75  i965_dri.so before
5014981   197160    27672  5239813   4ff405  i965_dri.so after

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler