gprs_ns2: rework logging of Rx and Tx NS PDU

Introduce 2 new logging sub systems for signal and unit data.
Unify log messages so all log messages look similiar.
Log also Rx PDUs. Ensure dropped Tx packets (BLOCK/RESET on SNS)
contain *Tx*.

Change-Id: I34b8fde2955ecc010d1dcd9512e1bba9211e2c0d
diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index 01850c4..343f976 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -122,7 +122,9 @@
 #define DLRSPRO		-19	/*!< Osmocom Remote SIM Protocol */
 #define DLNS		-20	/*!< Osmocom NS layer */
 #define DLBSSGP		-21	/*!< Osmocom BSSGP layer */
-#define OSMO_NUM_DLIB	21	/*!< Number of logging sub-systems in libraries */
+#define DLNSDATA	-22	/*!< Osmocom NS layer data pdus */
+#define DLNSSIGNAL	-23	/*!< Osmocom NS layer signal pdus */
+#define OSMO_NUM_DLIB	23	/*!< Number of logging sub-systems in libraries */
 
 /* Colors that can be used in log_info_cat.color */
 #define OSMO_LOGCOLOR_NORMAL NULL