Add support for uarts other than the serial console in TI OMAP SoCs.

Add support for uarts other than the serial console in TI OMAP SoCs.

The TI uart hardware is ns16550-compatible, except that before it can
be used the clocks and power have to be enabled and a non-standard
mode control register has to be set to put the device in uart mode
(as opposed to irDa or other serial protocols).  This adds the extra
code in an extension to the standard ns8250 probe routine, and the
rest of the driver is just the standard ns8250 code.