[XFRM]: Restrict authentication algorithm only when inbound transformation protocol is IPsec.

For Mobile IPv6 usage, routing header or destination options header is
used and it doesn't require this comparison. It is checked only for
IPsec template.

Based on MIPL2 kernel patch.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>