powerpc/5200: add support for charon board

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
[squashed with patch to add sm501 node]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Anatolij Gustschin <agust@denx.de>