* is equal to the 405GP SYS_CLK_FREQ. If not in bypass mode, check VCO
* to make sure it is within the proper range.
* spec: VCO = SYS_CLOCK x FBKDIV x PLBDIV x FWDDIV
* is equal to the 405GP SYS_CLK_FREQ. If not in bypass mode, check VCO
* to make sure it is within the proper range.
* spec: VCO = SYS_CLOCK x FBKDIV x PLBDIV x FWDDIV