drm/i915: add out_value to intel_wait_for_register_fw() and intel_de_wait_fw()

drm/i915: add out_value to intel_wait_for_register_fw() and intel_de_wait_fw()

Future users of intel_de_wait_fw() need the final value. Just return it
for everyone using intel_wait_for_register_fw() and intel_de_wait_fw()
to avoid adding or using another set of specialized functions. There
aren't that many users for these anyway.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/f804b2fe85ad63389e74d82e4c97220e9275f170.1748343520.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>