gsmtap.h: Define a packet type for encapsulation of GSM RLP frames

This allows us to feed RLP frames (occurring in GSM CSD) into wireshark
for dissection.

Change-Id: Ibb7f0731c31e5a5cd2911f733da5510ce0f3a1d6
diff --git a/src/core/gsmtap_util.c b/src/core/gsmtap_util.c
index 2e0b84e..a95c795 100644
--- a/src/core/gsmtap_util.c
+++ b/src/core/gsmtap_util.c
@@ -595,6 +595,7 @@
 	{ GSMTAP_TYPE_QC_DIAG,		"Qualcomm DIAG" },
 	{ GSMTAP_TYPE_LTE_NAS,		"LTE Non-Access Stratum" },
 	{ GSMTAP_TYPE_E1T1,		"E1/T1 lines" },
+	{ GSMTAP_TYPE_GSM_RLP,		"GSM Radio Link Protocol" },
 	{ 0, NULL }
 };