ASoC: rsnd: remove error pointer for adg->clkout[i]

commit d7f29819


("ASoC: rcar: fixup of_clk_add_provider() usage for multi clkout")
added adg->clkout[i] = ERR_PTR(-ENOENT),
but, adg->clkout[i] are assumed NULL or clk pointer.
This patch fix it.

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