drm/xe/pci: remove broken driver_release

This is quite broken since we are nuking the pdev link to the private
driver struct, but note here that driver_release is called when the
drm_device is released (poor mans drmm), which can be long after the
device has been removed. So here what we are actually doing is nuking
the pdev link for what is potentially bound to a different drm_device.
If that happens before our pci remove callback is triggered (for the new
drm_device) we silently exit and skip some important cleanup steps,
resulting in hilarity.

There should be no reason to implement driver_release, when we already
have nicer stuff like drmm, so just remove completely. The actual pdev
link is already nuked when removing the device.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522102143.128069-19-matthew.auld@intel.com