Add licence headers to NetworkStack AIDLs.

These are now output by the compiler. Update them now in their own
no-op CL so that future actual changes to the AIDL files are easier
to review.

Generated with:
$ m networkstack-aidl-interfaces-update-api
$ m ipmemorystore-aidl-interfaces-update-api

Test: m
Change-Id: I847aef51c7d27a9a886b2cad3b95bf82362a4411