ASoC: rcar: revert IOMMU support so far

commit 4821d914

 ("ASoC: rsnd: use dma_sync_single_for_xxx() for
IOMMU") had supported IOMMU, but it breaks normal sound "recorde"
and both PulseAudio's "playback/recorde". The sound will be noisy.

That commit was using dma_sync_single_for_xxx(), and driver should
make sure memory is protected during CPU or Device are using it.
But if driver returns current "residue" data size correctly on pointer
function, player/recorder will access to protected memory.

IOMMU feature should be supported, but I don't know how to handle it
without memory cache problem at this point.
Thus, this patch simply revert it to avoid current noisy sound.

Tested-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Tested-by: Ryo Kodama <ryo.kodama.vz@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>