Optimize two problems

a)Turn off low voltage detection register.During the esd test,
the low-voltage detection ic may be triggered to enter the slpin state,
so a black screen occurs on the panel.
b)Optimize CMD2 page1 gamma.
Signed-off-by: yangcong <yangcong5@huaqin.corp-partner.google.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211231045056.118640-1-yangcong5@huaqin.corp-partner.google.com