udf: improve error management in udf_CS0toUTF8()

udf_CS0toUTF8() now returns -EINVAL on error.
udf_load_pvoldesc() and udf_get_filename() do the same.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
index 41c3bef..35cc947 100644
--- a/fs/udf/unicode.c
+++ b/fs/udf/unicode.c
@@ -89,7 +89,7 @@
  * 				both of type "struct ustr *"
  *
  * POST-CONDITIONS
- *	<return>		Zero on success.
+ *	<return>		>= 0 on success.
  *
  * HISTORY
  *	November 12, 1997 - Andrew E. Mileski
@@ -112,7 +112,7 @@
 		memset(utf_o, 0, sizeof(struct ustr));
 		pr_err("unknown compression code (%d) stri=%s\n",
 		       cmp_id, ocu_i->u_name);
-		return 0;
+		return -EINVAL;
 	}
 
 	ocu = ocu_i->u_name;
@@ -350,7 +350,8 @@
 
 	udf_build_ustr_exact(unifilename, sname, slen);
 	if (UDF_QUERY_FLAG(sb, UDF_FLAG_UTF8)) {
-		if (!udf_CS0toUTF8(filename, unifilename)) {
+		ret = udf_CS0toUTF8(filename, unifilename);
+		if (ret < 0) {
 			udf_debug("Failed in udf_get_filename: sname = %s\n",
 				  sname);
 			goto out2;