This cleans up outputUsesInterrupts usage with rtems_termios_device_mode
enum values. The outputUsesInterrupts member was typed as an int, named
as if it were a boolean value, and used as if it were a
rtems_termios_device_mode enum. In this patch, values assigned to
outputUsesInterrupts have been converted to the corresponding
rtems_termios_device_mode enum value, conversions from
deviceOutputUsesInterrupts have been made explicit, and uses of
rtems_termios_device_mode enum values with deviceOutputUsesInterrupts
have been converted to booleans.
