drm/i915: Clean up the extra RPM ref on CHV with i915.enable_rc6=0

drm/i915: Clean up the extra RPM ref on CHV with i915.enable_rc6=0

Remove the CHV early bail out from intel_cleanup_gt_powersave() so that
we'll clean up the extra RPM reference held due to i915.enable_rc6=0.

Cc: Imre Deak <imre.deak@intel.com>
Fixes: b268c699aca5 ("drm/i915: refactor RPM disabling due to RC6 being disabled")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470136053-23276-1-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>