ARM: rpi: fix RPi1 board rev detection for warranty bit

Apparently the firmware's board rev response includes both the board
revision and some other data even on the RPi1. In particular, the
"warranty bit" is bit 24. We need to mask that out when looking up the
board ID.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

board/raspberrypi/rpi/rpi.c

@@ -278,10 +278,17 @@ static void get_board_rev(void)
 	 * https://github.com/pimoroni/RPi.version/blob/master/RPi/version.py
 	 * http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=99293&p=690282
 	 * (a few posts down)
+	 *
+	 * For the RPi 1, bit 24 is the "warranty bit", so we mask off just the
+	 * lower byte to use as the board rev:
+	 * http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=98367&start=250
+	 * http://www.raspberrypi.org/forums/viewtopic.php?f=31&t=20594
 	 */
 	rpi_board_rev = msg->get_board_rev.body.resp.rev;
 	if (rpi_board_rev & 0x800000)
 		rpi_board_rev = (rpi_board_rev >> 4) & 0xff;
+	else
+		rpi_board_rev &= 0xff;
 	if (rpi_board_rev >= ARRAY_SIZE(models)) {
 		printf("RPI: Board rev %u outside known range\n",
 		       rpi_board_rev);