ARM: mach-shmobile: add DMAC clock definitions on SH7372

These definitions are needed to let the runtime PM subsystem turn off
DMAC clocks, when it is suspended by the driver.

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