Make the initialization and polled functions independent of the Termios
context. This helps to implement the kernel I/O support without a dependency
on the Termios framework.
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.
Currently, zynq-uart code is always built and has some requirements for
BSPs that use it. Instead of making all BSPs satisfy that requirement or
working around it by setting defaults, this moves the zynq-uart code
into its own spec build object so it can be included if needed.
The zynq-uart set_attributes implementation was configured to always
return false which causes spconsole01 to fail. This restores the
disabled implementation which sets the baud rate registers
appropriately and allows spconsole01 to pass. This also expands the
set_attributes functionality to allow setting of the stop bits,
character width, and parity.
