Fix printf errors under -DDEBUG

Fix printf format-string/arg mismatches under -DDEBUG.

These warnings occur with DEBUG defined for a platform using
cpu/mpc85xx.  Users of other architectures can unearth similar
problems by adding the line "CFLAGS += -DDEBUG=1" in config.mk right
after "CFLAGS += $(call cc-option,-fno-stack-protector)".

Signed-off-by: Andrew Klossner <andrew@cesa.opbu.xerox.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>