drm/radeon: eliminate redundant connector_names table

connector_names table is just a repeat of information that
already exists in drm_connector_enum_list and the same string
can be retrieved using drm_get_connector_name function.

Nuke the redundant table and use the proper function to retrieve
the connector name.

Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>