drm/i915: Set .domains=POWER_DOMAIN_MASK for the always-on well

The always-on well is the same as runtime PM, so we should just
"enable" it for any power domain. Throw out the usless
FOO_ALWAYS_ON_DOMAINS defines and just use POWER_DOMAIN_MASK.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460977348-32260-2-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>