ASoC: wm9081: Fix reading wrong register for setting VMID 2*240k

VMID Divider Enable and Select is controlled by BIT[2:1] of WM9081_VMID_CONTROL
register (04h).
Current code reads wrong register (WM9081_BIAS_CONTROL_1) for setting
VMID 2*240k.

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