drm/amd/display: Populate invalid split index to be 0xF

[why]
There exists scenarios where the split index for subvp can be
pipe index 0. The assumption in FW is that the split index
won't be 0 but this is incorrect.

[how]
Instead populate non-split cases to be 0xF to differentiate
between split and non-split.
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@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/dc_dmub_srv.c

@@ -780,7 +780,7 @@ static void populate_subvp_cmd_pipe_info(struct dc *dc,
 	} else if (subvp_pipe->next_odm_pipe) {
 		pipe_data->pipe_config.subvp_data.main_split_pipe_index = subvp_pipe->next_odm_pipe->pipe_idx;
 	} else {
-		pipe_data->pipe_config.subvp_data.main_split_pipe_index = 0;
+		pipe_data->pipe_config.subvp_data.main_split_pipe_index = 0xF;
 	}
 
 	// Find phantom pipe index based on phantom stream
@@ -795,7 +795,7 @@ static void populate_subvp_cmd_pipe_info(struct dc *dc,
 			} else if (phantom_pipe->next_odm_pipe) {
 				pipe_data->pipe_config.subvp_data.phantom_split_pipe_index = phantom_pipe->next_odm_pipe->plane_res.hubp->inst;
 			} else {
-				pipe_data->pipe_config.subvp_data.phantom_split_pipe_index = 0;
+				pipe_data->pipe_config.subvp_data.phantom_split_pipe_index = 0xF;
 			}
 			break;
 		}