void ppc800_set_clock_freqs(unsigned extclk_freq, 
                            unsigned extal_freq, 
                            int is_extclk);

On a PPC 800 series chip, set the cpu_freq, timer_freq, and cycles_freq variables appropriately, given input frequencies of extclk_freq at the EXTCLK pin and extal_freq at the XTAL/EXTAL pins.

If is_extclk is nonzero, then the extclk_freq is used for the main timing reference (MODCLK1 signal is one at reset). If zero, extal_freq is used at the main timing reference (MODCLK1 signal is zero at reset).

Note that the setting of the frequency variables assumes that the ppc800_pit_init_qtime() routine is being used. If some other initialization of the qtime section and timer callouts takes place, the values in the frequency variables may have to be modified.