drm/amd/display: Reorder detect_edp_sink_caps before link settings read.

read_current_link_settings_on_detect() on eDP 1.4+ may use the
edp_supported_link_rates table which is set up by
detect_edp_sink_caps(), so that function needs to be called first.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Martin Leung <martin.leung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org