ASoC: wm9081: Don't write WM9081_BIAS_ENA bit to WM9081_VMID_CONTROL register

WM9081_BIAS_ENA is the bit[1] of WM9081_BIAS_CONTROL_1 register (05h).
Current code incorrectly write it to WM9081_VMID_CONTROL(04h) register.

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