sh: TMU platform data for sh7723

This patch adds TMU platform data for sh7723. Both clockevent
and clocksource support is enabled. While at it, adjust the
CMT clocksource rating to prioritize the TMU.

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