msm: mdss: dsi: fix lcd mode selection gpio config when display is off

When display is turned off, ensure that the lcd mode selection GPIO is
set to output LOW. This would prevent any current leakage from that GPIO
whenever display is off.

Change-Id: I91f636b2c1cc1890b4ca28f52e5190561bc5d927
CRs-Fixed: 1050785
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>