ASoC: rsnd: adg: check return value for rsnd_adg_get_clkin/out()

Current rsnd_adg_get_clkin/out() are void function,
thus adg->clk/clkout[i] might be NULL.

But, for_each_rsnd_clk/clkout() macros are assuming
all clks are non NULL.

Because of this mismatch, code can be complex and/or buggy.
These functions return error by this patch,
and make sure all clks are non NULL.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87pmx5i20m.wl-kuninori.morimoto.gx@renesas.com


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