pata_bf54x: fix return type of bfin_set_devctl

The new devctl func added for us to the driver has the wrong return
type.  Which is to say there shouldn't be any.  This fixes compile
time warnings as there shouldn't be any runtime difference.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>