link_rate and lane_count already configured in analogix_dp_set_link_train(),
so we don't need to config those repeatly after training finished, just
remove them out.

Beside Display Port 1.2 already support 5.4Gbps link rate, the maximum sets
would change from {1.62Gbps, 2.7Gbps} to {1.62Gbps, 2.7Gbps, 5.4Gbps}.
Tested-by: Caesar Wang <wxt@rock-chips.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>