ravb: Provide dev parameter to DMA API

This patch is in preparation for using this driver on arm64 where the
implementation of __dma_alloc_coherent fails if a device parameter is not
provided.

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Masaru Nagai <masaru.nagai.vx@renesas.com>
[horms: squashed into a single patch]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>