[crypto] Allow for extraction of ASN.1 algorithm parameters

[crypto] Allow for extraction of ASN.1 algorithm parameters

Some ASN.1 OID-identified algorithms require additional parameters,
such as an initialisation vector for a block cipher.  The structure of
the parameters is defined by the individual algorithm.

Extend asn1_algorithm() to allow these additional parameters to be
returned via a separate ASN.1 cursor.

Signed-off-by: Michael Brown <mcb30@ipxe.org>