ARM: tegra: Remove unused backlight-boot-off property

The backlight-boot-off property was proposed as a patch, but ended not
being accepted since different solution was already in the place:

    https://patchwork.kernel.org/project/linux-arm-kernel/patch/1406806970-12561-1-git-send-email-thierry.reding@gmail.com/#21327479Signed-off-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-paz00.dts

@@ -573,8 +573,6 @@ backlight: backlight {
 
 		brightness-levels = <0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 255>;
 		default-brightness-level = <10>;
-
-		backlight-boot-off;
 	};
 
 	clk32k_in: clock@0 {