[media] media-device: copy_to/from_user() returns positive

The copy_to/from_user() functions return the number of bytes *not*
copied.  They don't return error codes.

Fixes: 4f6b3f363475 ('media] media-device: add support for MEDIA_IOC_G_TOPOLOGY ioctl')

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>