Add Accessor functions for ARQ-II in EGPRS DL

Add accessor function in existing classes to support ARQ-II for
retransmission in EGPRS DL

Change-Id: Iefff956bf2dcfe8fb0b2f5a7a7a2122d5d555f9e
diff --git a/src/gprs_ms.h b/src/gprs_ms.h
index b07f175..bcc4fb3 100644
--- a/src/gprs_ms.h
+++ b/src/gprs_ms.h
@@ -86,6 +86,7 @@
 	uint8_t egprs_ms_class() const;
 	void set_ms_class(uint8_t ms_class);
 	void set_egprs_ms_class(uint8_t ms_class);
+	void set_current_cs_dl(GprsCodingScheme::Scheme scheme);
 
 	GprsCodingScheme current_cs_ul() const;
 	GprsCodingScheme current_cs_dl() const;