ARM: dts: kirkwood: fix audio for OpenRD clients

Fix audio on kirkwood-openrd-client:

1) The audio-controller was left disabled.

2) The probe fails because cs42l51 is missing #sound-dai-cells.

	/sound/simple-audio-card,codec: could not get #sound-dai-cells for /ocp@f1000000/i2c@11000/cs42l51@4a
	asoc-simple-card sound: parse error -22
	asoc-simple-card: probe of sound failed with error -22

3) The mapping is incorrect:

	asoc-simple-card sound: cs42l51-hifi <-> spdif mapping ok

   should be:

	asoc-simple-card sound: cs42l51-hifi <-> i2s mapping ok

Reported-by: Rick Thomas <rbthomas@pobox.com>
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Rick Thomas <rbthomas@pobox.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>