drm/amd/display: Don't read EDID in atomic_check

drm/amd/display: Don't read EDID in atomic_check

We shouldn't attempt to read EDID in atomic_check. We really shouldn't
even be modifying the connector object, or any other non-state object,
but this is a start at least.

Moving EDID cleanup to dm_dp_mst_connector_destroy from
dm_dp_destroy_mst_connector to ensure the EDID is still available for
headless mode.

Signed-off-by: Harry Wentland <[email protected]>
Reviewed-by: Tony Cheng <[email protected]>
Acked-by: Harry Wentland <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Cc: [email protected]