drm/msm/sde: populate display topology in atomic check

DRM client may read topology data after atomic commit even in
asynchronous mode. But kernel cannot promise real time update
of topology as the mode_set is executed in the commit thread.
This change identifies the topology for the given mode of the
display in the atomic_check and updates the topology property
of the connector.

Change-Id: I1bcdaa239f23d9636a83b9b33fa9b130bcbe97bd
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>