openssh: convert to Makefile.autotools.in and bump version to 5.1p1

This patch converts building of OpenSSH to use Makefile.autotools.in instead
and in the same process bump to latest upstream version 5.1p1.

The openssh.path is also cleaned up a bit to reflect the new release, i.e. some
of the patch is already applied/fixed upstream.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>