patch 9.0.1481: decrypting with libsodium may fail if the library changes

Problem:    Decrypting with libsodium may fail if the library changes.
Solution:   Add parameters used to the encrypted file header. (Christian
            Brabandt, closes #12279)
diff --git a/src/option.c b/src/option.c
index 4d9da47..1a9ba25 100644
--- a/src/option.c
+++ b/src/option.c
@@ -4274,7 +4274,7 @@
 		&& !curbufIsChanged() && curbuf->b_ml.ml_mfp != NULL)
 	{
 #ifdef FEAT_CRYPT
-	    if (crypt_get_method_nr(curbuf) == CRYPT_M_SOD)
+	    if (crypt_method_is_sodium(crypt_get_method_nr(curbuf)))
 		continue;
 #endif
 	    u_compute_hash(hash);