drm/xe: Remove xe_dummy_exit()

Since commit 014125c6 ("drm/xe: Support 'nomodeset' kernel
command-line option") the dummy exit is not needed anymore since the
caller check for a NULL pointer. Drop it.

Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250131223908.4147195-1-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>