package/openvpn: requires DES support in openssl

Enable DES in openssl to fix build failure raised since commit
a83d41867c8d69a77d5cd0a665aa216af5340359

Fixes:
 - http://autobuild.buildroot.org/results/a371f455d9550cb1593b5e349278082001245178

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/openvpn/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_OPENVPN
 	bool "openvpn"
 	depends on BR2_USE_MMU # fork()
 	select BR2_PACKAGE_OPENSSL if !BR2_PACKAGE_MBEDTLS
+	select BR2_PACKAGE_LIBOPENSSL_ENABLE_DES if BR2_PACKAGE_LIBOPENSSL
 	help
 	  OpenVPN is a full-featured SSL VPN solution which can
 	  accomodate a wide range of configurations, including road