[XFRM]: alg_key_len should be unsigned to avoid integer divides

alg_key_len is currently defined as 'signed int'. This unfortunatly
leads to integer divides in several paths.

Converting it to unsigned is safe and saves 208 bytes of text on i386.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/xfrm.h

@@ -92,7 +92,7 @@ struct xfrm_replay_state
 
 struct xfrm_algo {
 	char	alg_name[64];
-	int	alg_key_len;    /* in bits */
+	unsigned int	alg_key_len;    /* in bits */
 	char	alg_key[0];
 };