V4L/DVB (6753): Fix vivi to support non-zero minor node

There were a trouble at vivi driver when using non-zero inodes. This where due
to not properly preserving the minor inode after calling video_register. Since
this driver is a reference for newer drivers, and it is possible to have more
than one video device inside the machine, this patch makes vivi to dynamically
allocate video_device struct.

Thanks to Gregor Jasny <jasny@vidsoft.de> for pointing the issue.

Also, this patch removes a very anoying (but useless) message of not having a
proper release call.

CC: Gregor Jasny <jasny@vidsoft.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>