dmaengine: rcar-dmac: Use devm_platform_ioremap_resource()

This patch uses devm_platform_ioremap_resource() instead of
using platform_get_resource() and devm_ioremap_resource() together
to simplify.

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/1568010892-17606-4-git-send-email-yoshihiro.shimoda.uh@renesas.com


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