_RESET to specify reset vector address (ppc4xx reset vector is at end of
memory, rather than at beginning of ROM)
CONFIG_SYS_CLK_FREQ to specify frequency of system clock (needed for ppc4xx
clock speed calculation)
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1049 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1