msm: mdss: Delay overlay start until first update

Delay hardware initialization in the case of
hdmi until after after continuous splash
screen is completed. This delays iommu attach
and prevents corresponding page faults
caused by continuous splash screen use
of physical address.

Change-Id: Ia1f81544c7f32be1ac9e7513bb277ee88b612bed
Signed-off-by: Casey Piper <cpiper@codeaurora.org>