staging: usbip: properly handle "-l" / "--log" option

This option is in the long options list, and it's handled in the
option processing loop, but the optstring didn't include it.
Signed-off-by: Anthony Foiani <anthony.foiani@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/usbip/userspace/src/usbip.c

@@ -152,7 +152,7 @@ int main(int argc, char *argv[])
 	usbip_use_stderr = 1;
 	opterr = 0;
 	for (;;) {
-		opt = getopt_long(argc, argv, "+dt:", opts, NULL);
+		opt = getopt_long(argc, argv, "+dlt:", opts, NULL);
 
 		if (opt == -1)
 			break;