smpp: Move the coding/mode detection into a utils file
Make sure to not ever have issues with this code again, move the
utility code to a new file and create a basic testcase. The method
currently has 100% line and branch coverage. My initial patched
missed the smpp_utils.c file and I re-did the copying (and verifying
the branch coverage)
diff --git a/openbsc/tests/smpp/smpp_test.ok b/openbsc/tests/smpp/smpp_test.ok
new file mode 100644
index 0000000..fd44804
--- /dev/null
+++ b/openbsc/tests/smpp/smpp_test.ok
@@ -0,0 +1 @@
+Testing coding scheme support