serial: Make hw_stopped bool

Convert hw_stopped in uart_port to bool because its more appropriate
type for how it is used.

Also convert the local variable in uart_change_line_settings() caching
old hw_stopped to bool.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309080923.11778-7-ilpo.jarvinen@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>