Replace the BSP_CONSOLE_MINOR BSP option for the Xilinx Zynq BSPs with the new
BSP option ZYNQ_UART_KERNEL_IO_BASE_ADDR. Move the kernel I/O support to a
shared file.
Add <rtems/termiosdevice.h> which does not depend on <rtems/libio.h> to
provide rtems_termios_device_context and rtems_termios_device_handler.
For polled serial device drivers, this removes a header file dependency
to the full file system support.
