i965: Add new vtable entries for surface state updating functions.

i965: Add new vtable entries for surface state updating functions.

Gen7+ SURFACE_STATE is different from Gen4-6, so we need separate
per-generation functions for creating and updating it.  However, the
usage is the same, and callers just want to utilize the appropriate
functions with minimal pain.  So, put them in the vtable.

Since these take a brw_context pointer and are only used on Gen4, just
add a forward declaration.  This is the simplest (if not cleanest)
solution.  It would be nicer to have a i965-specific vtable, but that's
a refactor for another day.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>