Fix build of bsc-nat and GPRS code after include path change

The last patch changed the osmocore include paths, this fixes some build
problems caused by it
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c
index fe78ee9..2075ab6 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c
@@ -44,11 +44,11 @@
 #include <openbsc/socket.h>
 #include <openbsc/vty.h>
 
-#include <osmocom/core/gsm0808.h>
+#include <osmocom/gsm/gsm0808.h>
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/process.h>
 
-#include <osmocom/core/protocol/gsm_08_08.h>
+#include <osmocom/gsm/protocol/gsm_08_08.h>
 
 #include <osmocom/vty/telnet_interface.h>
 #include <osmocom/vty/vty.h>