package/libssh2: requires RIPEMD160 in openssl

package/libssh2: requires RIPEMD160 in openssl

Enable RIPEMD160 in openssl for libssh2 to avoid link time failure.

Fixes:
http://autobuild.buildroot.net/results/c6e031fca123865138d18c96d895778c03b639be/
http://autobuild.buildroot.net/results/4284098c0f29fdb7a4df9acbc23986e685c542d2/
http://autobuild.buildroot.net/results/a457bf27dfc0029cbfc2fdbf371aad1e2efa5b83/

Cc: Matt Weber <matthew.weber@collins.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>