ASoC: rsnd: move rsnd_gen_dma_addr() from gen.c to dma.c

Now, we have dma.c for Audio DMAC / Audio DMAC peri peri.
rsnd_gen_dma_addr() should go there.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>