ARM: bcm2835: add CPU node for ARM core

This patch adds the CPU node of the BCM2835 into the DT.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Eric Anholt <eric@anholt.net>