ARM: ux500: add an SMP enablement type and move cpu nodes

The "cpus" node cannot be inside the "soc" node, while this
works for the CoreSight blocks, the early boot code will look
for "cpus" directly under the root node, so this is a hard
convention. So move the CPU nodes.

Augment the "reg" property to match what is actually in the
hardware: 0x300 and 0x301 respectively.

Then add an SMP enablement type to be used by the SMP init
code, "ste,dbx500-smp".

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>