drm/i915/pps: Let calling intel_pps_vdd_{on, off}_unlocked() w/o PPS lock held

After a follow-up change on non-eDP outputs
intel_pps_vdd_{on,off}_unlocked() can be called without the PPS lock
held, allow for this.

Suggested-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250324180145.142884-2-imre.deak@intel.com