drm/qxl: Fix missing KMS poll cleanup

drm/qxl: Fix missing KMS poll cleanup

drm_kms_helper_poll_init() initializes the output polling work and
enables polling for the DRM device. qxl enables polling before calling
drm_dev_register(), but the drm_dev_register() failure path tears down
the modeset and device state without disabling the polling helper.

The remove path also unregisters and shuts down the DRM device without
first disabling the polling helper. Add matching drm_kms_helper_poll_fini()
calls in both paths so the delayed polling work is cancelled before qxl
tears down the associated modeset/device state.

Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 5ff91e442652 ("qxl: use drm helper hotplug support")
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260424112543.57819-1-mhun512@gmail.com