ARM: mach-shmobile: add SCIFA and SCIFB DMA slave definitions for sh7372

SH7372 can use DMA with the SCI serial driver. Add required slave IDs and slave
descriptors.

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