ARM: mach-shmobile: sh73a0 TMU support

Add support for 2 TMU timer channels on sh73a0.

One timer channel is used for clocksource and
the other is used for clockevents. All channels
in the same TMU block share MSTP bit as usual.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>