Revert "openssl: enable parallel build and installation"

This reverts commit 55e4ec05.

There are still build failures in parallel builds:
    http://autobuild.buildroot.org/results/9a0/9a0fc1064010a658155e6a18ec72e0e3c58ec7f6/
    http://autobuild.buildroot.org/results/c28/c28064f383da1f577bd9227d004f1939daf4579f/
    http://autobuild.buildroot.org/results/218/2180b9d900b27103acc92a2932f7ffa560b04831/


    and so on...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Ryan Barnett <rjbarnet@rockwellcollins.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>