ASoC: adau1701: Fix ADAU1701_SEROCTL_WORD_LEN_16 constant

The driver defines ADAU1701_SEROCTL_WORD_LEN_16 as 0x10 while it should be b10,
so 0x2. This patch fixes it.

Reported-by: Magnus Reftel <magnus.reftel@lockless.no>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org