ARM: shmobile: Specify device latencies for SH7372 devices directly

The results of adaptive latency computations in
GENPD_DEV_TIMED_CALLBACK() show that the start/stop and save/restore
state latencies of all devices on SH7372 I have tried are a little
below 250 us.  Therefore, if the 250 us is used as the common initial
value of the latency fields in struct gpd_timing_data for all devices
on SH7372, the latency values will never have to change at run time
and there won't be any overhead related to re-computation of the
corresponding PM QoS data.

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