video: bochs: Support a copy buffer

Provide support for using CONFIG_VIDEO_COPY with bochs, since this can
help to reduce flicker with QEMU

Signed-off-by: Simon Glass <sjg@chromium.org>
Series-to: u-boot
Series-links: 1:458274

drivers/video/bochs.c

@@ -81,7 +81,11 @@ static int bochs_init_fb(struct udevice *dev)
 	/* disable blanking */
 	bochs_vga_write(mmio, VGA_ATT_W - VGA_INDEX, VGA_AR_ENABLE_DISPLAY);
 
-	plat->base = fb;
+	/* Use double buffering if enabled */
+	if (IS_ENABLED(CONFIG_VIDEO_COPY) && plat->base)
+		plat->copy_base = fb;
+	else
+		plat->base = fb;
 
 	return 0;
 }