binutils: testsuite: fix duplicate testnames in readelf.exp

binutils: testsuite: fix duplicate testnames in readelf.exp

There are two places in readelf.exp where we generate duplicate
testnames.

The first is due to calling readelf_find_size twice with the same
iteration index (2).  This is fixed by using 4 for the second
instance.

The other is at the end of readelf_thin_archive_test.  This test calls
readelf_test before unconditionally passing.  It happens to construct
exactly the same test name as readelf test (might not be a
coincidence), so we end up with a duplicate test.  But it seems wrong
anyway to 'pass' a test that readelf_test might have failed, so simply
delete this duplicate pass entry.