drm/i915: use drm DP helper to read DPCD desc

Switch to using the common DP helpers instead of using our own.

v2: also remove leftover struct intel_dp_desc (Daniel)

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
3 files changed