drm/i915: Call encoder hotplug for init and resume cases

For all the encoders, call the hot_plug if it is registered.
This is required for connected boot and resume cases to generate
fake hpd resulting in reading of edid.
Removing the initial sdvo hot_plug call too so that it will be called
just once from this loop.

Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>