Extend esa_info_t struct

Extend esa_info_t struct

Add additional fields to the esa_info_t struct so the necessary data can
be passed from the keymat to the kernel ipsec interface, where ESA
creation and key generation using the TKM takes place.

The information is used during the inbound add_sa call to create an ESP
SA. This makes the hack of storing the local SPI in a kernel interface
variable between subsequent add_sa calls unnecessary.