Since rc_allocate_device() uses kmalloc, it can returns NULL,
so need to check,  otherwise, NULL derefenrece can happen.
Reported-by: NInsu Yun <wuninsu@gmail.com>
Signed-off-by: NSean Young <sean@mess.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>