CIPSO: Fix unaligned memory access in cipso_v4_gentag_hdr

We need to use put_unaligned when writing 32-bit DOI value
in cipso_v4_gentag_hdr to avoid unaligned memory access.

v2: unneeded type cast removed as Ondrej Mosnacek suggested.

Signed-off-by: Sergey Nazarov <s-nazarov@yandex.ru>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>