ASoC: wcd9320: Update headphone static gain in companding mode

Depending on the buik voltage, the static gain for headphone path
are different when compander is enabled. -3dB static gain is required
if the buik voltage is 1.8V and 0dB gain is required while the buik
voltage is 2.15V. Update the codec driver to match the requirement.

Change-Id: Ia21c8732362176d20956a817058ede3c4a472c52
CRs-Fixed: 500280
Signed-off-by: Kuirong Wang <kuirongw@codeaurora.org>