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 264981, 264983, 264985:

  The freescale imx uart driver works for the whole i.MX family, so rename
  the header file to not have "5xx" in the name.

  Flesh out imx_uart_init() so that we're not relying on u-boot to init
  the hardware (meaning uarts other than the console will work).

  Reword a comment block a bit.