rhashtable: Fix use before NULL check in bucket_table_free

Dan Carpenter reported a use before NULL check bug in the function
bucket_table_free.  In fact we don't need the NULL check at all as
no caller can provide a NULL argument.  So this patch fixes this by
simply removing it.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

lib/rhashtable.c

@@ -146,9 +146,7 @@ static void bucket_table_free(const struct bucket_table *tbl)
 	if (tbl->nest)
 		nested_bucket_table_free(tbl);
 
-	if (tbl)
 	kvfree(tbl->locks);
-
 	kvfree(tbl);
 }