drm/dp: note that DPCD 0x2002-0x2003 match 0x200-0x201

DP_SINK_COUNT_ESI and DP_DEVICE_SERVICE_IRQ_VECTOR_ESI0 have the same
contents as DP_SINK_COUNT and DP_DEVICE_SERVICE_IRQ_VECTOR,
respectively.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220104184857.784563-1-jani.nikula@intel.com