video: arm: rpi: Add brcm,bcm2708-fb compatible

When using CONFIG_OF_BOARD on rpi to use the dtb provided by the
RaspberryPi Fundation, the compatible string isn't the same, resulting
in not-functional video in u-boot.

Signed-off-by: Oleksandr Tymoshenko <gonzo@FreeBSD.org>
Signed-off-by: Emmanuel Vadot <manu@freebsd.org>

drivers/video/bcm2835.c

@@ -48,6 +48,7 @@ static int bcm2835_video_probe(struct udevice *dev)
 
 static const struct udevice_id bcm2835_video_ids[] = {
 	{ .compatible = "brcm,bcm2835-hdmi" },
+	{ .compatible = "brcm,bcm2708-fb" },
 	{ }
 };