coding: Add BER-reporting RACH decode functions

For all other decode operations we report the BER, but not for the
RACH.  This results in osmo-bts-trx not being able to report BER
to the higher layers, which is possible on other BTS backends.

Let's close this gap by introducing gsm0503_rach_ext_decode_ber()
and gsm0503_rach_decode_ber() with the usual n_errors / n_bits_total
arguments.

Change-Id: I2b1926a37bde860dcfeb0d613eb55a71271928c5
diff --git a/src/coding/libosmocoding.map b/src/coding/libosmocoding.map
index 95953cf..87b3886 100644
--- a/src/coding/libosmocoding.map
+++ b/src/coding/libosmocoding.map
@@ -110,8 +110,10 @@
 gsm0503_tch_ahs_decode;
 gsm0503_rach_ext_encode;
 gsm0503_rach_ext_decode;
+gsm0503_rach_ext_decode_ber;
 gsm0503_rach_encode;
 gsm0503_rach_decode;
+gsm0503_rach_decode_ber;
 gsm0503_sch_encode;
 gsm0503_sch_decode;