staging: memrar depends on RAR_REGISTER

Alan said that memrar should depend on RAR_REGISTER
(instead of selecting it).

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Ossama Othman <ossama.othman@intel.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>