i965/gen7: Refactor SF setup a bit to handle overrides in one place.

This is exactly analogous to Eric's Gen6 change in commit
e7280b16d634e1f434bebbce83996b3d30d0419c.

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

NOTE: This is a candidate for the 7.11 branch.
1 file changed