xfrm: alg_key_len & alg_icv_len should be unsigned

In commit ba749ae9 ([XFRM]: alg_key_len
should be unsigned to avoid integer divides
<http://git2.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commitdiff;h=ba749ae9>)
alg_key_len field of struct xfrm_algo was converted to unsigned int to
avoid integer divides.

Then Herbert in commit 1a6509d9


([IPSEC]: Add support for combined mode algorithms) added a new
structure xfrm_algo_aead, that resurrected a signed int for alg_key_len
and re-introduce integer divides.

This patch avoids these divides and saves 64 bytes of text on i386.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>