msm: mdss: Prevent AD configuration on HDMI path

Currently there is no use case for enabling AD on HDMI path. This check
is already present in mdss_ad_init_checks(), but that does not prevent
mdss_mdp_ad_setup() from being called. So invoke mdss_mdp_ad_setup() only
if display panel is not of HDMI type.

Change-Id: I175fcdbb0cc4ccda31d3fc8074b1e0213e0af10a
Signed-off-by: Ping Li <quicpingli@codeaurora.org>