ASoC: adau1701: fix adau1701_reg_read()

Fix a long standing bug in the read register routing of adau1701.
The bytes arrive in the buffer in big-endian, so the result has to be
shifted before and-ing the bytes in the loop.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org