drm/i915/dmc_wl: Allow enable_dmc_wl=3 to mean "always locked"

drm/i915/dmc_wl: Allow enable_dmc_wl=3 to mean "always locked"

When debugging issues that might be related to the DMC wakelock code, it
might be useful to compare runs with the lock acquired while DC states
are enabled vs the regular case. If issues disappear with the former, it
might be a symptom of something wrong in our code. Support having this
"always locked" behavior with enable_dmc_wl=3.

Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Reviewed-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241219221429.109668-5-gustavo.sousa@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>