openvpn: use conditional dependencies to avoid pulling in unused ssl libraries

Signed-off-by: Felix Fietkau <nbd@nbd.name>

package/network/services/openvpn/Makefile

@@ -37,8 +37,8 @@ define Package/openvpn/Default
   MAINTAINER:=Mirko Vogt <mirko@openwrt.org>
 endef
 
-Package/openvpn-openssl=$(call Package/openvpn/Default,openssl,OpenSSL,+libopenssl)
-Package/openvpn-mbedtls=$(call Package/openvpn/Default,mbedtls,mbedTLS,+libmbedtls)
+Package/openvpn-openssl=$(call Package/openvpn/Default,openssl,OpenSSL,+PACKAGE_openvpn-openssl:libopenssl)
+Package/openvpn-mbedtls=$(call Package/openvpn/Default,mbedtls,mbedTLS,+PACKAGE_openvpn-mbedtls:libmbedtls)
 Package/openvpn-nossl=$(call Package/openvpn/Default,nossl,plaintext (no SSL))
 
 define Package/openvpn/config/Default