ASoC: n810: fix init with DT boot

Since 3.14-rc1 only DT boot has been supported on N810, so this
file fails to init. Make a minimal fix to retain functionality.
This file should be properly converted to DT in longer term.

There seems to be still other unresolved issues with N810 audio support,
but this patch is needed at minimum as otherwise the machine driver
probing would completely fail.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>