ipv4: Fix unused variable warnings in fib_table_flush_external.

net/ipv4/fib_trie.c: In function ‘fib_table_flush_external’:
net/ipv4/fib_trie.c:1572:6: warning: unused variable ‘found’ [-Wunused-variable]
  int found = 0;
      ^
net/ipv4/fib_trie.c:1571:16: warning: unused variable ‘slen’ [-Wunused-variable]
  unsigned char slen;
                ^
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/fib_trie.c

@@ -1568,8 +1568,6 @@ void fib_table_flush_external(struct fib_table *tb)
 	struct fib_alias *fa;
 	struct tnode *n, *pn;
 	unsigned long cindex;
-	unsigned char slen;
-	int found = 0;
 
 	n = rcu_dereference(t->trie);
 	if (!n)