drm/i915/gen9+: Unify the HSW/BDW and GEN9+ power well helpers

drm/i915/gen9+: Unify the HSW/BDW and GEN9+ power well helpers

After the previous refactorings the HSW/BDW and GEN9+ power well helpers
are practically identical, so use the HSW power well helpers for GEN9+
too. This means using the HSW power well ops instead of the SKL one and
setting the irq_pipe_mask, has_vga and has_fuses attributes as needed.

v2:
- Rebased on v2 of patch 15.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170711204236.5618-7-imre.deak@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>