abis: Create a routine that can parse all SW Descriptions of a SW Config

Be able to parse the entire SW Config IE. Parse the SW Descruption
into a struct provided by the caller.
diff --git a/openbsc/tests/testsuite.at b/openbsc/tests/testsuite.at
index 8e12773..4c5de8d 100644
--- a/openbsc/tests/testsuite.at
+++ b/openbsc/tests/testsuite.at
@@ -43,3 +43,9 @@
 cat $abs_srcdir/si/si_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/si/si_test], [], [expout], [ignore])
 AT_CLEANUP
+
+AT_SETUP([abis])
+AT_KEYWORDS([abis])
+cat $abs_srcdir/abis/abis_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/abis/abis_test], [], [expout], [ignore])
+AT_CLEANUP