the check for i915_disable_power_well flag was removed by overlook,
so add it back now.
Reported-by: Paulo Zanoni <paulo.zanoni@intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>