MCS: move Mode enum outside of class definition

Move Mode (EDGE/GPRS) definition and related functions outside of
GprsCodingScheme class. This allows us to use standard libosmocore
value_string functions.

Change-Id: I3baaac7f1ca3f5b88917a23c1679d63847455f47
diff --git a/src/gprs_coding_scheme.cpp b/src/gprs_coding_scheme.cpp
index 53b3b07..1a89b77 100644
--- a/src/gprs_coding_scheme.cpp
+++ b/src/gprs_coding_scheme.cpp
@@ -198,7 +198,7 @@
 	return mcs_info[m_scheme].data_hdr;
 }
 
-void GprsCodingScheme::inc(Mode mode)
+void GprsCodingScheme::inc(enum mcs_kind mode)
 {
 	if (!isCompatible(mode))
 		/* This should not happen. TODO: Use assert? */
@@ -212,7 +212,7 @@
 	m_scheme = new_cs;
 }
 
-void GprsCodingScheme::dec(Mode mode)
+void GprsCodingScheme::dec(enum mcs_kind mode)
 {
 	if (!isCompatible(mode))
 		/* This should not happen. TODO: Use assert? */
@@ -254,16 +254,6 @@
 	m_scheme = CodingScheme(m_scheme - 1);
 }
 
-const char *GprsCodingScheme::modeName(Mode mode)
-{
-	switch (mode) {
-	case GPRS:       return "GPRS";
-	case EGPRS_GMSK: return "EGPRS_GMSK-only";
-	case EGPRS:      return "EGPRS";
-	default:         return "???";
-	}
-}
-
 bool GprsCodingScheme::isFamilyCompatible(GprsCodingScheme o) const
 {
 	if (*this == o)