clocksource: sh_cmt: One-off clockevent fix V2

Fix a one-off error in the CMT driver V2. The match register
should be programmed with the period minus one.

Many thanks to Eiraku-san for tracking down this issue.

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