[XFRM]: Add module alias for transformation type.

It is clean-up for XFRM type modules and adds aliases with its
protocol:
 ESP, AH, IPCOMP, IPIP and IPv6 for IPsec
 ROUTING and DSTOPTS for MIPv6

It is almost the same thing as XFRM mode alias, but it is added
new defines XFRM_PROTO_XXX for preprocessing since some protocols
are defined as enum.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Acked-by: Ingo Oeser <netdev@axxeo.de>
Signed-off-by: David S. Miller <davem@davemloft.net>