tbf: Remove IMSI handling from trigger_dl_ass

Currently the BTS::trigger_dl_ass() method assigns the IMSI to the MS
object. This should be (and is already) done earlier where the MS
object is retrieved/created.

This commit removes the corresponding code along with the 'imsi'
parameter from trigger_dl_ass.

Sponsored-by: On-Waves ehf
diff --git a/src/bts.cpp b/src/bts.cpp
index 371d369..f133977 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -471,7 +471,7 @@
 /* depending on the current TBF, we assign on PACCH or AGCH */
 void BTS::trigger_dl_ass(
 	struct gprs_rlcmac_dl_tbf *dl_tbf,
-	struct gprs_rlcmac_tbf *old_tbf, const char *imsi)
+	struct gprs_rlcmac_tbf *old_tbf)
 {
 	/* stop pending timer */
 	dl_tbf->stop_timer();
@@ -493,19 +493,14 @@
 		/* start timer */
 		tbf_timer_start(dl_tbf, 0, Tassign_pacch);
 	} else {
-		LOGP(DRLCMAC, LOGL_DEBUG, "Send dowlink assignment for %s on PCH, no TBF exist (IMSI=%s)\n", tbf_name(dl_tbf), imsi);
-		if (!imsi || strlen(imsi) < 3) {
-			LOGP(DRLCMAC, LOGL_ERROR, "No valid IMSI!\n");
-			return;
-		}
+		LOGP(DRLCMAC, LOGL_DEBUG, "Send dowlink assignment for %s on PCH, no TBF exist (IMSI=%s)\n", tbf_name(dl_tbf), dl_tbf->imsi());
 		dl_tbf->was_releasing = dl_tbf->state_is(GPRS_RLCMAC_WAIT_RELEASE);
 		/* change state */
 		dl_tbf->set_state(GPRS_RLCMAC_ASSIGN);
 		dl_tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_CCCH);
-		dl_tbf->assign_imsi(imsi);
 		dl_tbf->set_new_tbf(dl_tbf);
 		/* send immediate assignment */
-		dl_tbf->bts->snd_dl_ass(dl_tbf, 0, imsi);
+		dl_tbf->bts->snd_dl_ass(dl_tbf, 0, dl_tbf->imsi());
 		dl_tbf->m_wait_confirm = 1;
 	}
 }