lib/port.c: getttyuser(): Remove dead code

lib/port.c: getttyuser(): Remove dead code

port.pt_names cannot be NULL; it always points to the static array ttys.

$ grep -rn pt_names
lib/port.c:157:	port.pt_names = ttys;
lib/port.c:159:		port.pt_names[j] = cp;
lib/port.c:172:	port.pt_names[j] = NULL;
lib/port.c:344:		for (i = 0; NULL != port->pt_names[i]; i++) {
lib/port.c:345:			if (portcmp (port->pt_names[i], tty) == 0) {
lib/port.c:350:		if (port->pt_names[i] == 0) {
lib/port.h:39: *	pt_names - pointer to array of device names in /dev/
lib/port.h:45:	char **pt_names;

Signed-off-by: Alejandro Colomar <alx@kernel.org>