drm:msm:dsi: support additional gpios in display panel

Adding support for additional gpios for dsi display panel in xr smartviewer
reference device.

Change-Id: I8816b0244037bf48eee9be62cdcc2fd8bcd84cc6
Signed-off-by: Rajesh Bharathwaj <rajeshbharathwaj@codeaurora.org>