gsm0408_test: add a testcase for gsm48_decode_bearer_cap()

The new testcase contains a Bearer capability IE from Siemens S11E,
which does not use octet 3a (no extension bit set in octet 3).
gsm48_decode_bearer_cap() currently fails to parse it.

Change-Id: Ia19f3f6d80bc09ca3f8d39d35b148a0c0245141f
diff --git a/tests/gsm0408/gsm0408_test.err b/tests/gsm0408/gsm0408_test.err
new file mode 100644
index 0000000..1f0236c
--- /dev/null
+++ b/tests/gsm0408/gsm0408_test.err
@@ -0,0 +1,3 @@
+Incorrect decoded result of Speech, without octet 3a:
+ should: 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
+ is:     00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00