j1939acd: fix unused variable warning

open_socket() has a parameter to provide a network device name which
is properly assigned by its callers to s.intf in main().
Instead of using the callers value open_socket() directly accesses the
global s.intf which generates an unused variable warning with clang.

Fix this by using the provided parameter (no functional change).

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>

j1939acd.c

@@ -200,7 +200,7 @@ static int open_socket(const char *device, uint64_t name)
 			.addr = J1939_IDLE_ADDR,
 			.pgn = J1939_NO_PGN,
 		},
-		.can_ifindex = if_nametoindex(s.intf),
+		.can_ifindex = if_nametoindex(device),
 	};
 
 	if (s.verbose)