drm/udl: Kill pending URBs at suspend and disconnect

At both suspend and disconnect, we should rather cancel the pending
URBs immediately.  For the suspend case, the display will be turned
off, so it makes no sense to process the rendering.  And for the
disconnect case, the device may be no longer accessible, hence we
shouldn't do any submission.

Tested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220804075826.27036-4-tiwai@suse.de