A couple of drivers declare register_serial/unregister_serial prototypes
but don't use them.  FRV contains a commented out call to register_serial.
Since these are deprecated, remove these unnecessary references.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>