drm/i915/backlight: Disable pps power hook for aux based backlight

Pps power hook seems to be problematic for backlight controlled via
aux channel. Disable it for such cases.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3657


Cc: stable@vger.kernel.org
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220822140836.534432-1-jouni.hogander@intel.com