Eigen upstream was broken a little while ago, and it seemed to be
the case that we needed a fix for using the LLT factorization on
ARM.

This has been fixed and AFAIK there are no stable eigen releases
with this bug in it.

For full gore, see

http://eigen.tuxfamily.org/bz/show_bug.cgi?id=992

In light of the fix, the extra layer of indirection introduced earlier
is not needed and we are reverting to normal programming.

Change-Id: I16929d2145253b38339b573b27b6b8fabd523704