ARM: dts: re-fromat AT91 part to match other entries

The entries are separated as ARM V4/V5 and ARM V7 as some other per-SoC config
options may be removed in the near future.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Olof Johansson <olof@lixom.net>