ARM: shmobile: r8a7791: enable Audio DMAC peri peri via sound driver

Audio DMAC peri peri is no longer DMAEngine. it is supported by
sound driver. this patch enable it.

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