[media] vivid: fix error return code in vivid_create_instance()

Fix to return error code -ENOMEM from the memory or workqueue alloc
error handling case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>