Renesas sound card has "sampling rate convert" feature which
should be implemented via DPCM.
But, sound card driver point of view, it is difficult to add
this DPCM feature on simple-card driver. Especially, DT binding
support is very difficult.

This patch implements DPCM feature on DT as Renesas specific sound card.
This new driver is copied from current simple-card driver.
Main difference between simple-card and this driver are...
 1. removed unused feature from simple-card
 2. removed driver named prefix from DT property
 3. CPU will be FE, CODEC will be BE with snd-soc-dummy
 4. it supports sampling rate convert via .be_hw_params_fixup
 5. board specific routing is implemented in driver
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>