[POWERPC] 4xx: Add "amcc, haleakala" to the toplevel compatible property

Currently Haleakala uses the Kilauea platform code. This patch adds
"haleakala" to the compatible property, in case later kernel versions
will introduce a Haleakala platform code.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>