ARM: shmobile: Drop dev_irq_safe from R-mobile genpd config

The dev_irq_safe configuration is redundant, genpd don't have any
special treatmeant for handling it. Let's remove it.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>