msm: mdss: add debug prints for RT and NRT traffic

Currently there is no way to identify if a pipe is used for
real time or non real time traffic. Adding debug prints to
identify the same which would be helpful for debugging.

Change-Id: Id24bbe029ead66924c897ba81cfed50d4ce6217d
Signed-off-by: Radhika Ranjan Soni <rrsoni@codeaurora.org>