usb: r8a66597-udc: Fixed bufnum of Bulk

Signed-off-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Acked-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>