[media] staging/media: lirc_imon: fix leaks in imon_probe()

Error handling of usb_submit_urb() is not as all others in imon_probe().
It just unlocks mutexes and returns nonzero leaving all already
allocated resources unfreed.
The patch makes sure all the resources are deallocated.
Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>