don't pass argc in getopt32, it's superfluous

(add/remove: 0/0 grow/shrink: 12/131 up/down: 91/-727) Total: -636 bytes
   text    data     bss     dec     hex filename
 773469    1058   11092  785619   bfcd3 busybox_old
 772644    1058   11092  784794   bf99a busybox_unstripped

diff --git a/util-linux/losetup.c b/util-linux/losetup.c
index e2d4e4d..9409cdf 100644
--- a/util-linux/losetup.c
+++ b/util-linux/losetup.c
@@ -18,7 +18,7 @@
 	char *opt_o;
 	unsigned long long offset = 0;
 
-	opt = getopt32(argc, argv, "do:", &opt_o);
+	opt = getopt32(argv, "do:", &opt_o);
 	argc -= optind;
 	argv += optind;