Implement the Freescale i.MX UART.  This uart is used in a variety of
SoCs, including some by Motorola, as well as in the Freescale i.MX
series.

This patch gives only a `bare-bones' implementation, enough to run Linux
or OKL4, but that's about it.
Signed-off-by: NPhilip O'Sullivan <philipo@ok-labs.com>
Signed-off-by: NPeter Chubb <peter.chubb@nicta.com.au>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>