sh: CMT platform data for sh7720/sh7721

This patch adds CMT platform data for sh7720 and sh7721.
All 5 32-bit CMT channels unfortunately share a single IRQ.
Both clockevent and clocksource support is enabled.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>