serial: 8250_port: do not use goto for UPQ_NO_TXEN_TEST code flow

This is unnecessary here and makes the code harder to follow. Invert the
condition and drop the goto+label.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250317070046.24386-30-jirislaby@kernel.org


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