ARM: dts: msm: Enable backlight cooling device for SM6150

Add Display backlight cooling device for SM6150. Thermal framework
will mitigate the display brightness to achieve thermal cooling.

Change-Id: Ib5d49edb581fbc8a2749d0aabd4a0cbf03bc472b
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>