[binutils-gdb] readelf: handle corrupted chains better

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT 94d15024fe3dff908ab570aaa741b1c834c856d6 ***

Author: Mike Frysinger <vapier@gentoo.org>
Branch: master
Commit: 94d15024fe3dff908ab570aaa741b1c834c856d6

readelf: handle corrupted chains better
The current chain walker tries to protect itself against loops, by only
works with loops of length 1: a chain that points to itself.  If you have
a chain longer than that (3->4->3->4->...), readelf will still hang.

Since we know the max length of the chain, simply abort when we've walked
more times than that.  The only way that could have happened is if there
was a loop.