psbt: Use wallys function to check PST finalization status

Signed-off-by: Jon Griffiths <jon_p_griffiths@yahoo.com>

bitcoin/psbt.c

@@ -60,15 +60,12 @@ struct wally_psbt *new_psbt(const tal_t *ctx, const struct wally_tx *wtx)
 	return tal_steal(ctx, psbt);
 }
 
-bool psbt_is_finalized(struct wally_psbt *psbt)
+bool psbt_is_finalized(const struct wally_psbt *psbt)
 {
-	for (size_t i = 0; i < psbt->num_inputs; i++) {
-		if (!psbt->inputs[i].final_scriptsig &&
-				!psbt->inputs[i].final_witness)
-			return false;
-	}
-
-	return true;
+	size_t is_finalized;
+	int wally_err = wally_psbt_is_finalized(psbt, &is_finalized);
+	assert(wally_err == WALLY_OK);
+	return is_finalized ? true : false;
 }
 
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,

bitcoin/psbt.h

@@ -29,7 +29,7 @@ struct wally_psbt *new_psbt(const tal_t *ctx,
  * a psbt has the finalized script sig and/or witness data populated
  * for such a call
  */
-bool psbt_is_finalized(struct wally_psbt *psbt);
+bool psbt_is_finalized(const struct wally_psbt *psbt);
 
 struct wally_tx *psbt_finalize(struct wally_psbt *psbt, bool finalize_in_place);