abis_test: Fix the test case and calculate the right offset
We parse the load_config, take the ptrdiff_t from start and load_config
and from the previous array as the alignment can differ on different ABIs.
This was found by Daniel when executing the tests on a 64 bit userspace.
diff --git a/openbsc/tests/abis/abis_test.ok b/openbsc/tests/abis/abis_test.ok
index ba1da33..2f99f9d 100644
--- a/openbsc/tests/abis/abis_test.ok
+++ b/openbsc/tests/abis/abis_test.ok
@@ -7,10 +7,10 @@
Start: 13 len: 13
file_id: 09 07 05
file_ver: 06 07 08
-Start: 51 len: 26
+Start: 0 len: 26
file_id: 31 36 38 64 34 37 32 00
file_ver: 76 32 30 30 62 31 34 33 64 30 00
-Start: 77 len: 26
+Start: 26 len: 26
file_id: 31 36 38 64 34 37 32 00
file_ver: 76 32 30 30 62 31 34 33 64 31 00
SELECTED: 1