ARM: dts: mdss: add 8084 edp required parameters to dtsi

Add 8084 edp required configuration parameters to dtsi, such as
cont-splash-enable and GPIOs required by backlight.

CRs-Fixed: 661151
Change-Id: I7e3f09c557629612cad8084b7814bf029f30dd00
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>