drm/i915: apply phase pointer override on SNB+ too

These bits moved around on SNB and above.

v2: again with the git send-email fail
v3: add macros for getting per-pipe override & enable bits
v4: enable phase sync pointer on SNB and IVB configs as well

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>