drm/amd/display: Change AUX NACK behavior

[Why]
Retrying on receiving a NACK can result in long overall EDID read times
in some cases.

[How]
Retry only on DEFER and return immediately on NACK.

Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>