drm/i915/display: add module parameter to enable DMC wakelock

This feature should be disabled by default until properly tested and
mature.  Add a module parameter to enable the feature for testing,
while keeping it disabled by default for now.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412094148.808179-4-luciano.coelho@intel.com


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