Get rid of param 'poll' with constant value

Value 'false' is always passed by all callers of the function, so
there's no need to pass it. Furthermore, since it's false, there's no
need to access poll_fn since RRBP will always be invalid.

Change-Id: Ia48ce2a021865e76e813dedb22aca9c2522c5693
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index de32a1d..19415f1 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -616,7 +616,7 @@
 		/* send immediate assignment */
 		if ((pgroup = imsi2paging_group(imsi())) > 999)
 			LOGPTBFDL(this, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi());
-		bts_snd_dl_ass(bts, this, false, pgroup);
+		bts_snd_dl_ass(bts, this, pgroup);
 		m_wait_confirm = 1;
 	}
 }