drm/amd/display: Change swizzle visual confirm reference pipe

[Why]
To change the swizzle visual confirm reference pipe from top pipe to
bottom pipe due to bottom pipe information would be more important
for multiple overlay case.

Signed-off-by: Po-Ting Chen <[e-mail]>
Reviewed-by: Anthony Koo <[e-mail]>
Acked-by: Anson Jacob <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/core/dc_hw_sequencer.c

···
 		struct tg_color *color)
 {
 	uint32_t color_value = MAX_TG_COLOR_VALUE;
-	/* Determine the overscan color based on the top-most (desktop) plane's context */
-	struct pipe_ctx *top_pipe_ctx  = pipe_ctx;
+	/* Determine the overscan color based on the bottom-most plane's context */
+	struct pipe_ctx *bottom_pipe_ctx  = pipe_ctx;
 
-	while (top_pipe_ctx->top_pipe != NULL)
-		top_pipe_ctx = top_pipe_ctx->top_pipe;
+	while (bottom_pipe_ctx->bottom_pipe != NULL)
+		bottom_pipe_ctx = bottom_pipe_ctx->bottom_pipe;
 
-	switch (top_pipe_ctx->plane_state->tiling_info.gfx9.swizzle) {
+	switch (bottom_pipe_ctx->plane_state->tiling_info.gfx9.swizzle) {
 	case DC_SW_LINEAR:
 		/* LINEAR Surface - set border color to red */
 		color->color_r_cr = color_value;