ARM: dts: bcm283x: fix typo in mailbox address

The address of the mailbox node in the bcm283x.dtsi also has a typo.
So fix it accordingly.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Fixes: 05b682b7 ("ARM: bcm2835: dt: Add the mailbox to the device tree")
Signed-off-by: Eric Anholt <eric@anholt.net>

arch/arm/boot/dts/bcm283x.dtsi

@@ -104,7 +104,7 @@ rng@7e104000 {
 			reg = <0x7e104000 0x10>;
 		};
 
-		mailbox: mailbox@7e00b800 {
+		mailbox: mailbox@7e00b880 {
 			compatible = "brcm,bcm2835-mbox";
 			reg = <0x7e00b880 0x40>;
 			interrupts = <0 1>;