drm/amd/display: Move verify link cap after read edid

DP link layer test 400.1.1 fails intermittently.
The test device will pull hpd low immediately
after verify link cap.
Driver reads edid when hpd low that causes the test to fail.

Move read edid before verify link cap, so driver will
read edid before starting link training

Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>