drivers: sh: Leave disabling of unused PM domains to genpd

Since genpd at late init, will try to disable unused PM domains we
don't need to do it from here as well.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>