drm/udl: delete dead code

The "unode" pointer cannot be NULL here and checking for it causes
Smatch warnings:

   drivers/gpu/drm/udl/udl_main.c:259 udl_get_urb_locked()
   warn: can 'unode' even be NULL?

Fortunately, it's just harmless dead code which can be removed.  It's
left over from commit c5c354a3

 ("drm/udl: Fix inconsistent urbs.count
value during udl_free_urb_list()").

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/e0e35421-8746-43b6-971e-e25d1cd1d6a7@kili.mountain