misc: Fix compilation now that the method is located in libosmocore

These TLV helper functions are now located in libosmocore.
diff --git a/openbsc/configure.ac b/openbsc/configure.ac
index b56254c..1bb660f 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -53,7 +53,7 @@
 AM_CONDITIONAL(BUILD_SMPP, test "x$osmo_ac_build_smpp" = "xyes")
 
 
-PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 0.3.2)
+PKG_CHECK_MODULES(LIBOSMOCORE, libosmocore >= 0.5.3.60)
 PKG_CHECK_MODULES(LIBOSMOVTY, libosmovty >= 0.3.0)
 PKG_CHECK_MODULES(LIBOSMOGSM, libosmogsm >= 0.3.0)
 PKG_CHECK_MODULES(LIBOSMOABIS, libosmoabis >= 0.1.0)