drm/i915/dp: convert to struct intel_display

Going forward, struct intel_display is the main device data structure
for display. Switch to it internally in DP code.

v2/v3: Rebase

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d712a2894addde5fd7a8b593fbea87314df37e1f.1734083244.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>