sh: TMU: Introduce clocksource/clock events suspend/resume routines

Introduce suspend/resume routines for SH TMU clock source and
clock event device such that if those devices belong to a PM domain,
the generic PM domains framework will be notified that the given
domain may be turned off (during system suspend) or that it has to
be turned on (during system resume).

This change allows the A4R domain on SH7372 to be turned off during
system suspend (tested on the Mackerel board) if the TMU clock source
and/or clock event device is in use.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Magnus Damm <damm@opensource.se>