dmaengine: rcar-dmac: Use of_data values instead of a macro

Since we will have changed memory mapping of the DMAC in the future,
this patch uses of_data values instead of a macro to calculate
each channel's base offset.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Link: https://lore.kernel.org/r/1568010892-17606-3-git-send-email-yoshihiro.shimoda.uh@renesas.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>