[media] ddbridge: fix error handling in module_init_ddbridge()

If pci_register_driver() failed, resources allocated in
ddb_class_create() are leaked. The patch fixes it
as well as it replaces -1 with correct error code
in ddb_class_create().

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>