ASoC: rsnd: rename clk to clkin

Current adg.c is usig "clk" as clock IN, but is using "clkout" for
clock OUT. This patch arranges "clk" to "clkin".

This is prepare for R-Car Gen4 support.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87y1pi5emh.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>