openssl: use generic EVP_PKEY instead of RSA

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
openssl: use RSA_get_ex_new_index to have our own index

this supersede the finish override as we can detect free based on the
free callback of the data.

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>