gfx: drv: Clear all pending flips when a pipe is being disabled

gfx: drv: Clear all pending flips when a pipe is being disabled

When a pipe is disabled, no vblank interrupt will be generated, and thus
any pending flip will not complete on its own. Complete all pending
flips when the associated pipe is being disabled.

The drm_flip_driver initialization must be performed earlier since the
DPMS hooks get called during modeset init. Also fix the crtc/plane vs.
drm_flip_helper vs. drm_flip_driver cleanup order.

Issue: ANDROID-2302
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>