msm: mdss: add support for RT/NRT traffic

RT/NRT feature splits the AXI traffic over two AXI ports.
By diverting RT/NRT traffic to individual AXI ports, NRT
traffic can be throttled by NOC at SoC level based on AXI
port#. Having this capability can help tweak QoS based on
use-cases.
This change adds support to identify real time and
non-real time clients and acocrdingly program HW to take
care of routing the RT/NRT traffic to respective AXI ports.

Change-Id: Ic5d94423f125226539db9e21bc095dba803cc63e
Signed-off-by: Radhika Ranjan Soni <rrsoni@codeaurora.org>