bts: cosmetic: use DUMMY_VEC for padding where possible

Change-Id: I725a7bd1b0c4d2b0d73f1b6d1f16543bf3d9d9fe
diff --git a/src/bts.cpp b/src/bts.cpp
index 617cd78..22b4c08 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -884,7 +884,7 @@
 send_imm_ass_rej:
 	/* Allocate a bit-vector for RR Immediate Assignment [Reject] */
 	struct bitvec *bv = bitvec_alloc(22, tall_pcu_ctx); /* without plen */
-	bitvec_unhex(bv, "2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
+	bitvec_unhex(bv, DUMMY_VEC); /* standard '2B'O padding */
 
 	if (rc != 0) {
 		LOGP(DRLCMAC, LOGL_DEBUG, "Tx Immediate Assignment Reject on AGCH\n");
@@ -970,7 +970,7 @@
 
 	LOGPTBF(tbf, LOGL_INFO, "TX: START Immediate Assignment Downlink (PCH)\n");
 	bitvec *immediate_assignment = bitvec_alloc(22, tall_pcu_ctx); /* without plen */
-	bitvec_unhex(immediate_assignment, "2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
+	bitvec_unhex(immediate_assignment, DUMMY_VEC); /* standard '2B'O padding */
 	/* use request reference that has maximum distance to current time,
 	 * so the assignment will not conflict with possible RACH requests. */
 	LOGP(DRLCMAC, LOGL_DEBUG, " - TRX=%d (%d) TS=%d TA=%d pollFN=%d\n",