disp: msm: sde: set ctl preference for built in displays

Add changes to set CTL id preference for primary and secondary
builtin displays. This change check for preference if already set
from DT. If not preference will be set during connector init.
This avoids CTL datapath switches on secondary when there is dual
display usecase running concurrently with dp connect/disconnect.
In current issue scenario, due to the secondary ctl datapath
switch CTL_LAYER programming is happened on CTL_2 but CTL_FLUSH is
happened on CTL_1 causing pp_done timeout issues.

Change-Id: I5f1f52b7673740c48b249ab4d36e80b7a1d3db96
Signed-off-by: Jayaprakash Madisetty <jmadiset@codeaurora.org>