Add a function to get the frequency of the AHB bus. Another stopgap
function until we have full clock support for imx6.
The imx5x and imx6 chips have an onboard IOMUX device which also contains a
few "general purpose registers" whose values control chip behavior in ways
that have nothing to do with IO pin mux control. Define a simple API that
other soc-specific code can use to read and write the registers, and provide
the imx51 implementation of them.
Fix a typo.
c691dc79ec