debian/control + SPEC: Add missing build dependency to libosmo-abis

In I6b93809b5ac7d01af55888347dd787b0bc997ae1 we introduced E1 support
to osmo-mgw, but failed to add it to the build dependencies of the
Debian packages, making network:osmocmo:nightly builds fail.

Change-Id: I45717bda3ef7eba1ef59b993cc8a69bf2f92a29f
2 files changed