ASoC: sh: fsi: Add runtime PM support

This patch add support runtime PM.
Driver callbacks for Runtime PM are empty because
the device registers are always re-initialized after
pm_runtime_get_sync(). The Runtime PM functions replaces the
clock framework module stop bit handling in this driver.

Signed-off-by: Kuninori Morimoto <morimoto.kuninori@renesas.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>