ARM: dts: msm: remove backlight control type from adv panel

ADV7533 is a DSI to HDMI bridge chip, it does not need any backlight
control to be defined. So removing this property from panel dt files.

Change-Id: I3ca7290ce324d9385da8b13d9c141de0730d8535
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>