openssl: use generic EVP_PKEY instead of RSA

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
openssl: add dsa support

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
openssl: add ecdsa support

Tested-By: Sanaullah <sanaullah82@gmail.com>
Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>