ARM: dts: pxa2xx: drop #address-cells and #size-cells from /cpus

PXA is single-core only, so this node will not have enumerable children.
Drop the #address-cells and #size-cells properties to squelch a dtc warning.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>