msm: mdss: update init code of auo panel

Set VGH to 6V, avoid screen slightly flickers
when enter idle mode.

BUG:25462016
Change-Id: I5d05a65e81447928fc91e28e0441af92227d133c
Signed-off-by: l00212897 <gang.li@huawei.com>
(cherry picked from commit 47e2b0d2)