sh: Add SCIF2 support for SH7763.

SH7763 has 3 SCIF device. Current code supports SCIF0 and 1.
SCIF0 and 1 are same register constitution, but only SCIF2 is different.
I added support of SCIF2.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu.nobuhiro@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>