jffs2: Replace zero-length array with flexible-array

There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code should
always use “flexible array members”[1] for these cases. The older style of
one-element or zero-length arrays should no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://github.com/KSPP/linux/issues/21Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

fs/jffs2/nodelist.h

@@ -259,7 +259,7 @@ struct jffs2_full_dirent
 	uint32_t ino; /* == zero for unlink */
 	unsigned int nhash;
 	unsigned char type;
-	unsigned char name[0];
+	unsigned char name[];
 };
 
 /*

fs/jffs2/summary.h

@@ -61,7 +61,7 @@ struct jffs2_sum_dirent_flash
 	jint32_t ino; 		/* == zero for unlink */
 	uint8_t nsize;		/* dirent name size */
 	uint8_t type;		/* dirent type */
-	uint8_t name[0];	/* dirent name */
+	uint8_t name[];	/* dirent name */
 } __attribute__((packed));
 
 struct jffs2_sum_xattr_flash
@@ -117,7 +117,7 @@ struct jffs2_sum_dirent_mem
 	jint32_t ino; 		/* == zero for unlink */
 	uint8_t nsize;		/* dirent name size */
 	uint8_t type;		/* dirent type */
-	uint8_t name[0];	/* dirent name */
+	uint8_t name[];	/* dirent name */
 } __attribute__((packed));
 
 struct jffs2_sum_xattr_mem