drm/msm/sde: add sde_connector kickoff trigger callbacks

Add a callback into the connector framework to allow sending
per-frame parameters at kickoff time. Specifically, this is
needed to support the partial update feature where only a subset
region of interest is updated on the display.

Change-Id: I4a6982a33110e5b114a60b92926d43c8aced950d
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>