ARM: dts: msm: add DT property for RT/NRT feature for 8939

RT/NRT feature identifies the real time and non-real time
clients and accordingly programs the HW to take care of
routing the RT/NRT traffic to respective AXI ports.
Add DT property to enable this feature for msm8939.

Change-Id: I27aa73992e17905825275a528349382f4a679339
Signed-off-by: Radhika Ranjan Soni <rrsoni@codeaurora.org>