ARM: shmobile: r8a7790: add Audio DMAC support

R-Car H2 has many DMACs
(ex SYS-DMAC, 2D-DMAC, Audio-DMAC, USB-DMAC etc)
and, these DMAEngine needs DMA slave IDs to use it.

This patch adds new DMA slave ID list for r8a7790.
There, common part has RCAR_DMA_xxx prefix,
and Audio DMAC part has AUDIO_DMAC_SLAVE_xxx prefix.

Audio DMAC can be controlled via sh-dma-engine

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>