ARM: shmobile: add common DMAEngine definitions

Current shmobile have DMAEngine specific settings on each CPU code,
but SH-ARM DMAC use same value.

This patch adds new dma-register.h header to share definitions
and reduce a waste of code on SH-ARM architecture.

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>