powerpc/44x: Add reset-type to katmai.dts

Katmai needs "reset-type" = "chip reset" (2) to correctly reboot the
board.

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