ssb_calc_clock_rate
baud_base = ssb_calc_clock_rate(plltype,
rate = ssb_calc_clock_rate(pll_type, n, m);
rate = ssb_calc_clock_rate(plltype, clkctl_n, clkctl_m);
extern u32 ssb_calc_clock_rate(u32 plltype, u32 n, u32 m);