msm: mdss: fix to reduce rotator bandwidth

Rotator path needs to consider 60fps whenever
traffic shapper is not enabled. Add change
to use this frame rate if traffic shaper is
not in use.

Change-Id: I70a28a36be4894e4a8874bcda5fb23363ca843cc
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>