drm/i915: Init power domains early in driver load

drm/i915: Init power domains early in driver load

Since

commit d1f6a3c7f7d7f36a04a02449415baa51e6d81171
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Fri Nov 27 18:55:26 2015 +0200

    drm/i915: Introduce a gmbus power domain

gmbus also needs the power domain infrastructure right from the start,
since as soon as we register the i2c controllers someone can use them.

v2: Adjust cleanup paths too (Chris).

v3: Rebase onto -nightly (totally bogus tree I had lying around) and
also move dpio init head (Ville).

v4: Ville instead suggested to move gmbus setup later in the sequence,
since it's only needed by the modeset code.

v5: Move even close to the actual user, right next to the comment that
states where we really need gmbus (and interrupts!).

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Meelis Roos <mroos@linux.ee>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: d1f6a3c7f7d7 ("drm/i915: Introduce a gmbus power domain")
Cc: stable@vger.kernel.org
References: http://www.spinics.net/lists/intel-gfx/msg83075.html
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452682528-19437-1-git-send-email-daniel.vetter@ffwll.ch
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>