PCU: introduce f_rrbp_ack_fn(), fix poll frame number calculation

The resulting frame number shall be within the period of TDMA hyperframe.

Change-Id: I794a14f69293cbbc937d62d09dd5794956b882db
Signed-off-by: Vadim Yanitskiy <axilirator@gmail.com>
diff --git a/library/RLCMAC_Templates.ttcn b/library/RLCMAC_Templates.ttcn
index 38147f3..bcd2b23 100644
--- a/library/RLCMAC_Templates.ttcn
+++ b/library/RLCMAC_Templates.ttcn
@@ -29,6 +29,11 @@
 		return 0;
 	}
 
+	function f_rrbp_ack_fn(uint32_t current_fn, MacRrbp rrbp)
+	return uint32_t {
+		return (current_fn + f_rrbp_fn_delay(rrbp)) mod 2715648;
+	}
+
 	function f_rlcmac_mcs2headertype(CodingScheme mcs) return EgprsHeaderType {
 		select (mcs) {
 		case (MCS_0) { return RLCMAC_HDR_TYPE_3; }