drm/i915/ddi: For an active output call the DP encoder sync_state() only for DP

If the DDI encoder output is enabled in HDMI mode there is no point in
calling intel_dp_sync_state(), as in that case the DPCD initialization
will fail - as expected - with AUX timeouts. Prevent calling the hook in
this case.

Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-5-imre.deak@intel.com