dt-bindings: arm: add SMP enable-method for BCM2836

This adds a compatible string "brcm,bcm2836-smp" for Broadcom's
BCM2836 and BCM2837 to the 32 bit ARM CPU device tree binding.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/cpus.txt

@@ -200,6 +200,7 @@ described below.
 			    "arm,realview-smp"
 			    "brcm,bcm11351-cpu-method"
 			    "brcm,bcm23550"
+			    "brcm,bcm2836-smp"
 			    "brcm,bcm-nsp-smp"
 			    "brcm,brahma-b15"
 			    "marvell,armada-375-smp"