drm/i915/dmc_wl: Sanitize enable_dmc_wl according to hardware support

Instead of checking for HAS_DMC_WAKELOCK() multiple times, let's use it
to sanitize the enable_dmc_wl parameter and use that variable when
necessary.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241108130218.24125-15-gustavo.sousa@intel.com