msm: mdss: send FB registered event before initializing MDP

Send the FB registered event before initializing MDP in order to
allow the panel driver to complete any internal initialization
before MDP operations begin. For example, in the case of HDMI
panels, this will ensure that the Hot Plug Detection (HPD)
circuitry is enabled and that the HDCP libraries are loaded
before data is transmitted on the link.

Change-Id: Icbf1e0abb937d4196677aa896a5386fbaa8ae034
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>