i965/surface_state: Rename brw_update to gen4_update
i965/surface_state: Rename brw_update to gen4_update

We're about to add generic versions which work across gens and those should
have the brw name.

Signed-off-by: Jason Ekstrand <68c46a606457643eab92053c1c05574abb26f861@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <749697f19798b7f640b17221fd283b903825f071@intel.com>
Reviewed-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler