drm/xe/display: Fix double mutex initialization

drm/xe/display: Fix double mutex initialization

All of these mutexes are already initialized by the display side since
commit 3fef3e6ff86a ("drm/i915: move display mutex inits to display
code"), so the xe shouldn´t initialize them.

Fixes: 44e694958b95 ("drm/xe/display: Implement display support")
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240405200711.2041428-1-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>