MFC r271055, r271084, r271094:

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.

MFC 264977:

Stop calling imx51_ccm_foo() clock functions from imx6 code. Instead
define a few imx_ccm_foo() functions that are implemented by the imx51
or imx6 ccm code.

MFC r261410

Follow r261352 by updating all drivers which are children of simplebus
to check the status property in their probe routines.

MFC r257383, r257384:

Add some bare-bones support for enabling usb and usbphy clocks.

Add a "no-op" USB PHY driver for imx-family SoCs.

MFC r256774:

Clock divisors 0-3 correspond to dividing by 1-4, so add 1 before dividing.

MFC r271055, r271084, r271094:

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.

MFC 264977:

Stop calling imx51_ccm_foo() clock functions from imx6 code. Instead
define a few imx_ccm_foo() functions that are implemented by the imx51
or imx6 ccm code.

MFC r261410

Follow r261352 by updating all drivers which are children of simplebus
to check the status property in their probe routines.

MFC r257383, r257384:

Add some bare-bones support for enabling usb and usbphy clocks.

Add a "no-op" USB PHY driver for imx-family SoCs.

MFC r256774:

Clock divisors 0-3 correspond to dividing by 1-4, so add 1 before dividing.