drm/i915/hsw+: Unify the hsw/bdw and gen9+ power well req/state macros

drm/i915/hsw+: Unify the hsw/bdw and gen9+ power well req/state macros

Although on HSW/BDW there is only a single display global power well,
it's programmed the same way as other GEN9+ power wells. This also
means we can get at the HSW/BDW request and status flags the same way
it's done on GEN9+ by assigning the corresponding HSW/BDW power well ID.
This ID was assigned in a recent patch, so we can now switch to using
the same macros everywhere on HSW+.

Updating the HSW power well control register with RMW is not strictly
necessary, but this will allow us to use the same code for GEN9+.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1499352040-8819-13-git-send-email-imre.deak@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>