cmp: initialize limit to avoid stack garbage limits

Approved by:	re (gjb)
Pointy hat:	kevans
Fixes:	4e380e8474 ("cmp: add -n, --bytes to limit number of bytes [...]")
Sponsored by:	Klara, Inc.

(cherry picked from commit f1f7f31366)
(cherry picked from commit aba2dc46df)

usr.bin/cmp/cmp.c

@@ -105,7 +105,7 @@ main(int argc, char *argv[])
 	bool special;
 	const char *file1, *file2;
 
-	skip1 = skip2 = 0;
+	limit = skip1 = skip2 = 0;
 	oflag = O_RDONLY;
 	while ((ch = getopt_long(argc, argv, "+bhi:ln:sxz", long_opts, NULL)) != -1)
 		switch (ch) {