talloc: revert to use talloc inside libosmocore

It's not a good idea to confuse the two changes with each other.  Moving the
Abis part into a separate library is independent from the question whether we
have talloc inside libosmocore or use a stand-alone talloc library.
diff --git a/tests/e1inp_ipa_bts_test.c b/tests/e1inp_ipa_bts_test.c
index b62afed..d2a21f9 100644
--- a/tests/e1inp_ipa_bts_test.c
+++ b/tests/e1inp_ipa_bts_test.c
@@ -1,5 +1,5 @@
 #include <stdio.h>
-#include <talloc.h>
+#include <osmocom/core/talloc.h>
 #include <string.h>
 #include <unistd.h>
 #include <osmocom/abis/abis.h>