[asn1] Rename ASN1_OID_CURSOR to ASN1_CURSOR

There is nothing OID-specific about the ASN1_OID_CURSOR macro.  Rename
to allow it to be used for constructing ASN.1 cursors with arbitrary
contents.

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

src/crypto/mishmash/rsa_sha224.c

@@ -37,7 +37,7 @@ struct asn1_algorithm sha224_with_rsa_encryption_algorithm __asn1_algorithm = {
 	.name = "sha224WithRSAEncryption",
 	.pubkey = &rsa_algorithm,
 	.digest = &sha224_algorithm,
-	.oid = ASN1_OID_CURSOR ( oid_sha224_with_rsa_encryption ),
+	.oid = ASN1_CURSOR ( oid_sha224_with_rsa_encryption ),
 };
 
 /** SHA-224 digestInfo prefix */