Return boolean from ->carrier_raised() instead of 0 and 1. Make the
return type change also to tty_port_carrier_raised() that makes the
->carrier_raised() call (+ cd variable in moxa into which its return
value is stored).

Also cleans up a few unnecessary constructs related to this change:

	return xx ? 1 : 0;
	-> return xx;

	if (xx)
		return 1;
	return 0;
	-> return xx;
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # For MMC
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230117090358.4796-7-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>