disp: msm: sde: avoid connector state mode update

There is a race condition between sdm thread and display thread, when
sdm thread may be accessing the mode_info field while duplicating the
connector state, display thread may be updating the current mode info.
This would lead to the next commit using invalid mode and could cause
wrong hw configuration.
This change removes copying the mode_info in encoder struct while
atomic check phase and also removes accessing the connector mode_info
during mode_set. The encoder struct is now updated at the mode_set
with the cached connector mode.

Change-Id: I069ed592ec017ce4aa5c9c94b340bf94c5e1ebff
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>
Signed-off-by: Samantha Tran <samtran@codeaurora.org>