ARM: shmobile: sh73a0: add DMAEngine support for MPDMAC

Current shdmac can support MPDMAC (= sound DMA) on sh73a0.
This support reduce CPU load when sound was playback.

On v2.0 manual, MPDMAC MID/RID number were wrong.
This patch is using the number which seems correct.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>