ASoC: wm8711: Fix wrong mask for setting input audio data bit length select

The Input Audio Data Bit Length Select is controlled by BIT[3:2] of
WM8711_IFACE(07h) register.
Current code incorrectly masks BIT[1:0] which is for Audio Data Format Select.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@kernel.org