ASoC: wm8737: Fixup setting VMID Impedance control register

According to the datasheet:
R10 (0Ah) VMID Impedance Control

BIT 3:2 VMIDSEL DEFAULT 00

DESCRIPTION: VMID impedance selection control
00: 75kΩ output
01: 300kΩ output
10: 2.5kΩ output

WM8737_VMIDSEL_MASK is 0xC (VMIDSEL - [3:2]),
so it needs to left shift WM8737_VMIDSEL_SHIFT bits for setting these bits.

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