rpi: link to another model number info source

This source has been blessed by Dom Cobley at the RPi Foundation, so seems
like the best source to refer to. It's a superset of and consistent with
the other sources.

Cc: Lubomir Rintel <lkundrak@v3.sk>
Cc: Eric Anholt <eric@anholt.net>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

board/raspberrypi/rpi/rpi.c

@@ -78,6 +78,11 @@ struct msg_get_clock_rate {
  * http://raspberryalphaomega.org.uk/2013/02/06/automatic-raspberry-pi-board-revision-detection-model-a-b1-and-b2/
  * http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=32733
  * http://git.drogon.net/?p=wiringPi;a=blob;f=wiringPi/wiringPi.c;h=503151f61014418b9c42f4476a6086f75cd4e64b;hb=refs/heads/master#l922
+ *
+ * In http://lists.denx.de/pipermail/u-boot/2016-January/243752.html
+ * ("[U-Boot] [PATCH] rpi: fix up Model B entries") Dom Cobley at the RPi
+ * Foundation stated that the following source was accurate:
+ * https://github.com/AndrewFromMelbourne/raspberry_pi_revision
  */
 struct rpi_model {
 	const char *name;