ARM: dts: msm: set HS mode to read ESD register for dsi_hx8399_truly_cmd

This display panel should use HS mode to read ESD register, LP
mode could not get the right register value.

Change-Id: I9a165f19bd2774523ba716d24d22261dd398fa88
Signed-off-by: Yuan Zhao <yzhao@codeaurora.org>