Move extended PDP logging macro to header

It might be useful for any user of libgtp who uses libosmocore so let's
make generalized version of it available as part of installable header.

Change-Id: I79aba10ef989384a28f059c30899e65c771ae5e1
Related: SYS#3610
diff --git a/TODO-RELEASE b/TODO-RELEASE
index e38e18c..1009c44 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -8,3 +8,4 @@
 # If any interfaces have been removed or changed since the last public release: c:r:0.
 #library	what		description / commit summary line
 libgtp		pdp.h		Addition of new tx_gpdu_seq struct member member
+libgtp		pdp.h		add LOGPDPX() helper to public API
diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index 780a0c2..462b395 100644
--- a/ggsn/ggsn.c
+++ b/ggsn/ggsn.c
@@ -83,8 +83,7 @@
 #define LOGPGGSN(level, ggsn, fmt, args...)			\
 	LOGP(DGGSN, level, "GGSN(%s): " fmt, (ggsn)->cfg.name, ## args)
 
-#define LOGPPDP(level, pdp, fmt, args...)			\
-	LOGP(DGGSN, level, "PDP(%s:%u): " fmt, imsi_gtp2str(&(pdp)->imsi), (pdp)->nsapi, ## args)
+#define LOGPPDP(level, pdp, fmt, args...) LOGPDPX(DGGSN, level, pdp, fmt, ## args)
 
 static int ggsn_tun_fd_cb(struct osmo_fd *fd, unsigned int what);
 static int cb_tun_ind(struct tun_t *tun, void *pack, unsigned len);
diff --git a/gtp/pdp.h b/gtp/pdp.h
index f8b0df8..106d544 100644
--- a/gtp/pdp.h
+++ b/gtp/pdp.h
@@ -17,6 +17,9 @@
 
 struct gsn_t;
 
+#define LOGPDPX(ss, level, pdp, fmt, args...)				\
+	LOGP(ss, level, "PDP(%s:%u): " fmt, imsi_gtp2str(&(pdp)->imsi), (pdp)->nsapi, ## args)
+
 #define PDP_MAX 1024		/* Max number of PDP contexts */
 #define PDP_MAXNSAPI 16		/* Max number of NSAPI */