msm: mdss: add systrace begin/end trace events

Adding trace points for systrace at various points in
the driver.

Change-Id: I4783fd2982bddb7f111de9e064bcaff153eb1ce1
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>
Signed-off-by: Vineet Bajaj <vbajaj@codeaurora.org>