Replace a dependency for px5g with openssl-util. Both LEDE and Openwrt have now uhttpd versions that can generate keys with OpenSSL cmd tools if px5g is not found. This change enables an "OpenSSL-only" version of LuCI without mbedTLS/PolarSSL. (Note: if px5g is found, uhttpd will prefer that.) Relevant commits in uhttpd: LEDE:3c4858eeb282132540a39097dc5ad8Openwrt:6ec32832d2Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>