drm/amd/display: decide link training settings based on channel coding

[how]
Rename initialize_training_settings to decide_training_settings.
Call get link encoding format and decide training settings
based on current channel coding.

Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>