serial: sh-sci: Add overrun handling of SCIFA and SCIFB

SCIFA and SCIFB can detect the overrun, but it does not support.
This adds overrun handling of SCIFA and SCIFB.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>