mpc5200_cdm_get_ipb_freq
uint32_t mpc5200_cdm_get_ipb_freq(void);
sc->sc_ipb_freq = mpc5200_cdm_get_ipb_freq();
ipb = mpc5200_cdm_get_ipb_freq(); /* never returns zero */
uint32_t ipb = mpc5200_cdm_get_ipb_freq();
u_int div = psc_baud_divisor(mpc5200_cdm_get_ipb_freq(), baud);