drm/msm/dsi-staging: add mdp transfer time as mode property

Add mdp transfer time to mode property blob since it is now defined per
mode in the dtsi files. Also at boot modes are not populated until the
first commit, thus mdp transfer time in connector capability blob is 0
and this causes userspace to read an invalid value.

Change-Id: I1c20c4e154ffbfc1001e76ac32ca1b1598dbd844
Signed-off-by: Amine Najahi <anajahi@codeaurora.org>