gsm/protocol/gsm_04_08.h: add gsm48_meas_res_is_valid()

Change-Id: Iae2bd508a08c4b5093d36e514c22218763e11edf
diff --git a/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index 3fa9419..ea77e76 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -593,6 +593,12 @@
 #endif
 } __attribute__ ((packed));
 
+/*! Check if the given mr contains valid measurement results */
+static inline bool gsm48_meas_res_is_valid(const struct gsm48_meas_res *mr)
+{
+	return (mr->meas_valid == 0); /* 0 means valid */
+}
+
 /* Chapter 10.5.2.21aa */
 struct gsm48_multi_rate_conf {
 #if OSMO_IS_LITTLE_ENDIAN