gprs/sgsn_mm_ctx_alloc(): initialize MM state to IDLE

Previous the state was only set in Iu mode.

Change-Id: I99a6aec1090cad9b9d38d134cc9b34ef292062df
diff --git a/openbsc/src/gprs/gprs_sgsn.c b/openbsc/src/gprs/gprs_sgsn.c
index 6d49e19..260e032 100644
--- a/openbsc/src/gprs/gprs_sgsn.c
+++ b/openbsc/src/gprs/gprs_sgsn.c
@@ -223,6 +223,7 @@
 	ctx->ran_type = MM_CTX_T_GERAN_Gb;
 	ctx->gb.tlli = tlli;
 	ctx->gmm_state = GMM_DEREGISTERED;
+	ctx->pmm_state = MM_IDLE;
 	ctx->auth_triplet.key_seq = GSM_KEY_SEQ_INVAL;
 	ctx->ciph_algo = sgsn->cfg.cipher;
 	LOGMMCTXP(LOGL_DEBUG, ctx, "Allocated with %s cipher.\n",