ASoC: rcar: fixup of_clk_add_provider() usage for multi clkout

Current adg is calling of_clk_add_povider() multiple times,
but it is not correct usage. This patch fixup its parameter
and call it once.

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