drm/msm/sde: fix the output fence trigger offset

The output fence trigger offset should be set based on
the type of display. This information is currently
derived from the encoder attached to the crtc. Get this
info from the atomic state instead of the encoder as the
crtc/encoder connection might not have happened at this
point leading to wrong assumption in the display-type.

Change-Id: I72ed74ba4e0a9f2c3678fdb7e708042bf64781b2
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>