staging: meilhaus, switch to misc device

There is no need to occupy one major number because of one device.

Switch to misc device, which also emits uevent, so that the dev node
is also created by udev.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: David Kiliani <mail@davidkiliani.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>