drm/xe: Move drm_dev_unplug() out of display function

drm/xe: Move drm_dev_unplug() out of display function

This is not really display-related and needed for any sequence on driver
removal that has to interact with drm_dev_enter()/drm_dev_exit().
Just remove xe_device_remove_display() and inline it in the single
caller to make clear this is not done only for display.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250213192909.996148-10-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>