gprs/gprs_mm: add value_strings for PMM & MM states

Change-Id: I4e34dcd5e48c4dd73d63c6f865298ee7d9c864be
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 9f1e9f0..1718861 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -105,6 +105,15 @@
 	},
 };
 
+static const struct value_string gprs_pmm_state_names[] = {
+	{ PMM_DETACHED,		"PMM DETACH" },
+	{ PMM_CONNECTED,	"PMM CONNECTED" },
+	{ PMM_IDLE,		"PMM IDLE" },
+	{ MM_IDLE,		"MM IDLE" },
+	{ MM_READY,		"MM READY" },
+	{ MM_STANDBY,		"MM STANDBY" },
+};
+
 static int gsm48_gmm_authorize(struct sgsn_mm_ctx *ctx);
 
 static void mmctx_timer_cb(void *_mm);
@@ -129,7 +138,9 @@
 	if (ctx->pmm_state == state)
 		return;
 
-	LOGMMCTXP(LOGL_INFO, ctx, "Changing PMM state from %i to %i\n", ctx->pmm_state, state);
+	LOGMMCTXP(LOGL_INFO, ctx, "Changing PMM state from %s to %s\n",
+		  get_value_string(gprs_pmm_state_names, ctx->pmm_state),
+		  get_value_string(gprs_pmm_state_names, state));
 
 	switch (state) {
 	case PMM_IDLE:
@@ -153,7 +164,9 @@
 	if (ctx->pmm_state == state)
 		return;
 
-	LOGMMCTXP(LOGL_INFO, ctx, "Changing MM state from %i to %i\n", ctx->pmm_state, state);
+	LOGMMCTXP(LOGL_INFO, ctx, "Changing MM state from %s to %s\n",
+		  get_value_string(gprs_pmm_state_names, ctx->pmm_state),
+		  get_value_string(gprs_pmm_state_names, state));
 
 	switch (state) {
 	case MM_READY: