Rename as_{dl,ul}_tbf -> tbf_as_{dl,ul}_tbf

Prefix the function accordingly to specify the input object.

Change-Id: I225568fe2cb5236817cdd9609354c24c66723606
diff --git a/src/bts.cpp b/src/bts.cpp
index e72f4c7..ae63a12 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1234,7 +1234,7 @@
 	    poll->tbf_poll.poll_tbf->direction != GPRS_RLCMAC_UL_TBF)
 		goto no_tbf;
 
-	tbf = as_ul_tbf(poll->tbf_poll.poll_tbf);
+	tbf = tbf_as_ul_tbf(poll->tbf_poll.poll_tbf);
 	/* we need to distinguish TA information provided by L1
 	 * from PH-DATA-IND and PHY-RA-IND so that we can properly
 	 * update TA for given TBF