drm/i915/dp: Correct the order of deletion for ghost eDP devices

The order of the calls does matter indeed.  Swapping the call order of
intel_dp_destroy() and intel_dp_encoder_destroy() fixes the problem.
This is because i2c_del_adapter unregisters the device which parent is
intel_connector, and connectors are removed in intel_dp_destroy().  Thus
intel_dp_encoder_destroy() must be called before intel_dp_destroy().

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=24822


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Keith Packard <keithp@keithp.com>