Modify the SH MTU2 clock event device driver to support runtime PM at
a basic level (i.e. device clocks can be disabled and enabled, but
domain power must be on, because the device has to be marked as
"irq safe").
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Magnus Damm <damm@opensource.se>