arm64: renesas: salvator-common: fixup audio_clkout

"audio_clkout" is dummy clock of <&rcar_sound 0> to avoid clock loop
which invites probe conflict. Thus <&rcar_sound 0> and "audio_clkout"
should be same value.

On commit 5e2feac3 ("arm64: renesas: salvator-common: sound
clock-frequency needs descending order") exchanged <&rcar_sound 0>,
but it didn't modify "audio_clkout".
This patch fixup it.

Fixes: 5e2feac3

 ("arm64: renesas: salvator-common: sound clock-frequency needs descending order")
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>