drm/msm/sde: fix connector list iteration in timeline_status

A change ported from a previous kernel version
did not include calls to the new and necessary
list iter begin and end APIs when iterating a drm
connector list. Adding these new APIs prevents
memory corruption while iterating lists.

Change-Id: Ie1d0ab5930fc961eba0a408e30d3287945340bc4
Signed-off-by: Fuad Hossain <fhossain@codeaurora.org>