MCS: add mcs_is_*() helpers

In preparation for Channel Coding Command encoder in follow-up patches
let's add necessary helpers. Those are similar to previously used
helpers from GprsCodingScheme class but without CamelCase and with less
typo chances between Gprs and Egprs cases.

Change-Id: I6699cbc8d7ae766fa4d2b3d37e5f9ff1cf158b7e
diff --git a/src/coding_scheme.c b/src/coding_scheme.c
index 135ddd2..4a5d0d4 100644
--- a/src/coding_scheme.c
+++ b/src/coding_scheme.c
@@ -46,6 +46,24 @@
 	return get_value_string(mcs_names, val);
 }
 
+bool mcs_is_gprs(enum CodingScheme cs)
+{
+	return CS1 <= cs && cs <= CS4;
+}
+
+bool mcs_is_edge(enum CodingScheme cs)
+{
+	return MCS1 <= cs && cs <= MCS9;
+}
+
+bool mcs_is_edge_gmsk(enum CodingScheme cs)
+{
+	if (mcs_is_edge(cs))
+		return cs <= MCS4;
+
+	return false;
+}
+
 static struct {
 	struct {
 		uint8_t data_header_bits;