x86: edison: Add the rest of UARTs present on board

x86: edison: Add the rest of UARTs present on board

Intel Edison has three UART ports, i.e.
 port 0 - Bluetooth
 port 1 - auxiliary, available for general purpose use
 port 2 - debugging, usually console output is here

Enable all of them for future use.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>