migration: Export tls.c functions in its own file

Just for the functions exported from tls.c.  Notice that we can't
remove the migration/migration.h include from tls.c because it access
directly MigrationState for the tls params.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
5 files changed