aufs: minor, use FAM

In linux v5.7-rc2, zero-length array declarations are replaced by FAM
(flexible-array member),
	a2008395fe2e 2020-04-18 dirent.h: Replace zero-length array with flexible-array member

Aufs simply follows this trend.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
(cherry picked from commit 747a01ec1835988fa20177789a6fb65c5198fcb9)

fs/aufs/dir.h

@@ -25,7 +25,7 @@ struct au_nhash {
 
 struct au_vdir_destr {
 	unsigned char	len;
-	unsigned char	name[0];
+	unsigned char	name[];
 } __packed;
 
 struct au_vdir_dehstr {

fs/aufs/dirren.c

@@ -571,7 +571,7 @@ struct au_drinfo_rev_elm {
 struct au_drinfo_rev {
 	unsigned char			already;
 	aufs_bindex_t			nelm;
-	struct au_drinfo_rev_elm	elm[0];
+	struct au_drinfo_rev_elm	elm[];
 };
 
 /* todo: isn't it too large? */

include/uapi/linux/aufs_type.h

@@ -274,7 +274,7 @@ struct au_rdu_ent {
 	uint8_t		type;
 	uint8_t		nlen;
 	uint8_t		wh;
-	char		name[0];
+	char		name[];
 } __aligned(8);
 
 static inline int au_rdu_len(int nlen)
@@ -325,7 +325,7 @@ struct au_drinfo {
 		uint8_t oldnamelen;
 		uint64_t _padding;
 	};
-	uint8_t oldname[0];
+	uint8_t oldname[];
 } __aligned(8);
 
 struct au_drinfo_fdata {
@@ -419,7 +419,7 @@ union aufs_brinfo {
 	struct {
 		int16_t	id;
 		int	perm;
-		char	path[0];
+		char	path[];
 	};
 } __aligned(8);