sh: also without PM_RUNTIME pm_runtime.o must be built

When CONFIG_PM_RUNTIME is off, drivers/sh/pm_runtime.o still has to be
built on sh platforms, because then it provides means to statically
switch on device PM clocks.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>