DMA: shdma: add a header with common for ARM SoCs defines

All shdma DMACs on ARM SoCs share certain register layout patterns, which
are currently defined in arch/arm/mach-shmobile/include/mach/dma-register.h.
That header is included by SoC-specific setup-*.c files to be used in DMAC
platform data. That header, however, cannot be directly used by the driver.
This patch copies those defines into a driver-local header to be used by
Device Tree configurations.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>