drm/i915: Move gt/pm irq handling out from irq disabled section on VLV

No need to actually handle the GT/PM interrupt while we have interrupt
sources disabled. Move the actual processing to happen after we've
restored VLV_IER and master interrupt enable.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460571598-24452-11-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>