[XFRM]: alg_key_len & alg_icv_len should be unsigned

In commit ba749ae98d5aa9d2ce9a7facde0deed454f92230 ([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=ba749ae98d5aa9d2ce9a7facde0deed454f92230>) 
alg_key_len field of struct xfrm_algo was converted to unsigned int to 
avoid integer divides.

Then Herbert in commit 1a6509d991225ad210de54c63314fd9542922095 
([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 <redacted>