secure_seq: fix sparse errors

Fixes following warnings :

net/core/secure_seq.c:125:28: warning: incorrect type in argument 1
(different base types)
net/core/secure_seq.c:125:28:    expected unsigned int const [unsigned]
[usertype] a
net/core/secure_seq.c:125:28:    got restricted __be32 [usertype] saddr
net/core/secure_seq.c:125:35: warning: incorrect type in argument 2
(different base types)
net/core/secure_seq.c:125:35:    expected unsigned int const [unsigned]
[usertype] b
net/core/secure_seq.c:125:35:    got restricted __be32 [usertype] daddr
net/core/secure_seq.c:125:43: warning: cast from restricted __be16
net/core/secure_seq.c:125:61: warning: restricted __be16 degrades to
integer

Fixes: 7cd23e53 ("secure_seq: use SipHash in place of MD5")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>