drm/i915: Remove special case for power well 1/MISC_IO state verification

Even though PW#1 and the MISC_IO power wells are managed by the
DMC firmware (toggled dynamically if conditions allow it) from the
driver's POV they are always on if the display core is initialized
(always restored by DMC to the enabled state after exiting from DC5/6
for instance b/c of MMIO access). Accordingly we can just mark them as
always-on and remove the special casing for them during state
verification (thus enabling verification for these power wells too).

Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181109145822.15446-3-imre.deak@intel.com