drm/amd/display: Remove SW w/a for HDCP 1.4 1A-07 failure based on ECO fix

[why]
W/a no longer needed

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Oliver Logush <oliver.logush@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>