drm/msm/sde: initialize display info during connector setup

SDE connector queries each display driver for display_info to
setup its connector. This change initializes the display info
struct to handle invalid display_info queries.

Change-Id: Ibb84b21e76790f32cf19d963245587984013eb3b
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>