drm/amd/display: use link_rate_set above DPCD 1.3 (#1527)

drm/amd/display: use link_rate_set above DPCD 1.3 (#1527)

[Why & How]
According to eDP spec, DPCD 1.3 is only for eDP DPCD v1.4
In dpcd_set_link_settings function, the driver is just above v1.3

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: ChiawenHuang <chiawen.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>