drm/amd/display: not abort link train when bw is low

[WHY]
DP tunneling should not abort link train even bandwidth become
too low after downgrade. Otherwise, it would fail compliance test.

[HOW}
Do link train with downgrade settings even bandwidth is not enough

Reviewed-by: Cruise Hung <cruise.hung@amd.com>
Reviewed-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Signed-off-by: Peichen Huang <PeiChen.Huang@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c

@@ -1789,13 +1789,10 @@ bool perform_link_training_with_retries(
 			is_link_bw_min = ((cur_link_settings.link_rate <= LINK_RATE_LOW) &&
 				(cur_link_settings.lane_count <= LANE_COUNT_ONE));
 
-			if (is_link_bw_low) {
+			if (is_link_bw_low)
 				DC_LOG_WARNING(
 					"%s: Link(%d) bandwidth too low after fallback req_bw(%d) > link_bw(%d)\n",
 					__func__, link->link_index, req_bw, link_bw);
-
-				return false;
-			}
 		}
 
 		msleep(delay_between_attempts);