drm/i915/dp: use native encoder ->mode_set callback
drm/i915/dp: use native encoder ->mode_set callback

Usual drill applies. Again I've not switched the upcast helpers to use
intel_encoder instead of drm_encoder since that's much more invasive
and will change also the hdmi and ddi encoders.

Reviewed-by: Rodrigo Vivi <f714145d6ee82178e54021e0c168f56d17b53c9c@gmail.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs