edge: Select implementation by mode in rlc_data_to_dl_append

Currently the GPRS data block encoding is applied to every
coding scheme, even if an MCS is selected.

This commit renames the actual encoding function to
rlc_data_to_dl_append_gprs (not exported) and puts
selection code into Encoding::rlc_data_to_dl_append. This
requires an additional cs argument.

Sponsored-by: On-Waves ehf
diff --git a/src/encoding.h b/src/encoding.h
index 9b4b09e..4c35757 100644
--- a/src/encoding.h
+++ b/src/encoding.h
@@ -22,6 +22,7 @@
 
 #include <stdint.h>
 #include <gsm_rlcmac.h>
+#include <gprs_coding_scheme.h>
 
 struct gprs_rlcmac_bts;
 struct gprs_rlcmac_tbf;
@@ -86,7 +87,7 @@
 	};
 
 	static AppendResult rlc_data_to_dl_append(
-		struct gprs_rlc_data_block_info *rdbi,
+		struct gprs_rlc_data_block_info *rdbi, GprsCodingScheme cs,
 		gprs_llc *llc, int *offset, int *num_chunks,
 		uint8_t *data,
 		bool is_final);