tty: serial: extend lqasc_tx_ready() to lqasc_console_putchar()

tty: serial: extend lqasc_tx_ready() to lqasc_console_putchar()

There is one more place where lqasc_tx_ready() can be used now:
lqasc_console_putchar(). So replace the open-coded variant by the
helper.

Suggested-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220927111819.18516-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>