ASoC: Build adau1701 when SND_SOC_ALL_CODECS is selected

The adau1701 driver was removed from SND_SOC_ALL_CODECS in commit commit ee8c7e97
("ASoC: Remove adau1701 from SND_SOC_ALL_CODECS due to Sigma dependency") due
to the dependency on the SigmaDSP firmware loader which was only available on a
limited set of platforms. This was fixed quite some time ago in commit 40216ce7
("ASoC: Move SigmaDSP firmware loader to ASoC") though, so we can add the driver
back again to SND_SOC_ALL_CODECS.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>