tbf/bts: Rename tbf->snd_dl_ack to tbf->rcvd_dl_ack

This function is called to act upon a received DL ACK packet so this
name makes more sense.
diff --git a/src/bts.cpp b/src/bts.cpp
index ff16e29..6c02408 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -805,7 +805,7 @@
 	LOGP(DRLCMAC, LOGL_DEBUG, "RX: [PCU <- BTS] %s Packet Downlink Ack/Nack\n", tbf_name(tbf));
 	tbf->poll_state = GPRS_RLCMAC_POLL_NONE;
 
-	rc = tbf->snd_dl_ack(
+	rc = tbf->rcvd_dl_ack(
 		ack_nack->Ack_Nack_Description.FINAL_ACK_INDICATION,
 		ack_nack->Ack_Nack_Description.STARTING_SEQUENCE_NUMBER,
 		ack_nack->Ack_Nack_Description.RECEIVED_BLOCK_BITMAP);
diff --git a/src/tbf.cpp b/src/tbf.cpp
index d6b3802..b20d0fc 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -1425,7 +1425,7 @@
 	return 0;
 }
 
-int gprs_rlcmac_tbf::snd_dl_ack(uint8_t final_ack, uint8_t ssn, uint8_t *rbb)
+int gprs_rlcmac_tbf::rcvd_dl_ack(uint8_t final_ack, uint8_t ssn, uint8_t *rbb)
 {
 	LOGP(DRLCMACDL, LOGL_DEBUG, "%s downlink acknowledge\n", tbf_name(this));
 
diff --git a/src/tbf.h b/src/tbf.h
index c301960..24b98d2 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -103,7 +103,7 @@
 	struct msgb *create_dl_ass(uint32_t fn);
 	struct msgb *create_ul_ass(uint32_t fn);
 	struct msgb *create_ul_ack(uint32_t fn);
-	int snd_dl_ack(uint8_t final, uint8_t ssn, uint8_t *rbb);
+	int rcvd_dl_ack(uint8_t final, uint8_t ssn, uint8_t *rbb);
 	int snd_ul_ud();
 
 	/* blocks were acked */