ARM: shmobile: r8a7791: Add Audio DMAC devices to DT

Instantiate the two Audio DMA controllers in the r8a7791 device tree.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
[geert: corrected spelling of audmac1]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>