ARM: dts: msm: Adding mac-address entry for sdx55

Current dtsi does not support mac address. So random
address is being assigned to the interface. To overcome this
we have added the dtsi entry for the same.

Change-Id: I308d085372280ac13c6b201950413c6978813232
Acked-by: Abhishek Chauhan <abchauha@qti.qualcomm.com>
Signed-off-by: Sunil Paidimarri <hisunil@codeaurora.org>