drm/i915/display: tie DMC wakelock to DC5/6 state transitions

We only need DMC wakelocks when we allow DC5 and DC6 states.  Add the
calls to enable and disable DMC wakelock accordingly.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412094148.808179-5-luciano.coelho@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>