MCS: move HeaderType enum outside of class definition

Move functions which compute number of blocks or bits depending on
header type and corresponding enum outside of GprsCodingScheme
class. This will allows us to use standard libosmocore value_sting
functions in upcoming patches for IA Rest Octet encoding/decoding.

Change-Id: Id0873f85e1f16a72e17e7fbc4ad76b194917067f
diff --git a/src/encoding.cpp b/src/encoding.cpp
index 019de52..58df95f 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -1118,7 +1118,7 @@
 	unsigned int bsn_delta;
 
 	switch(cs.headerTypeData()) {
-	case GprsCodingScheme::HEADER_GPRS_DATA:
+	case HEADER_GPRS_DATA:
 		gprs = static_cast<struct rlc_dl_header *>
 			((void *)data);
 
@@ -1134,7 +1134,7 @@
 		gprs->bsn   = rlc->block_info[0].bsn;
 		break;
 
-	case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_1:
+	case HEADER_EGPRS_DATA_TYPE_1:
 		egprs1 = static_cast<struct gprs_rlc_dl_header_egprs_1 *>
 			((void *)data);
 
@@ -1173,7 +1173,7 @@
 		data[offs] = (data[offs] & 0b11110011) | e_fbi_header;
 		break;
 
-	case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_2:
+	case HEADER_EGPRS_DATA_TYPE_2:
 		egprs2 = static_cast<struct gprs_rlc_dl_header_egprs_2 *>
 			((void *)data);
 
@@ -1197,7 +1197,7 @@
 		data[offs] = (data[offs] & 0b11001111) | e_fbi_header;
 		break;
 
-	case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_3:
+	case HEADER_EGPRS_DATA_TYPE_3:
 		egprs3 = static_cast<struct gprs_rlc_dl_header_egprs_3 *>
 			((void *)data);