fs: Replace zero-length array with flexible-array member

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://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays

Signed-off-by: Gustavo A. R. Silva <[e-mail]>

fs/binfmt_elf.c

···
 	struct elf_thread_core_info *next;
 	struct task_struct *task;
 	struct elf_prstatus prstatus;
-	struct memelfnote notes[0];
+	struct memelfnote notes[];
 };
 
 struct elf_note_info {

fs/hfs/btree.h

···
 	wait_queue_head_t lock_wq;
 	atomic_t refcnt;
 	unsigned int page_offset;
-	struct page *page[0];
+	struct page *page[];
 };
 
 #define HFS_BNODE_ERROR		0

fs/hfsplus/hfsplus_fs.h

···
 	wait_queue_head_t lock_wq;
 	atomic_t refcnt;
 	unsigned int page_offset;
-	struct page *page[0];
+	struct page *page[];
 };
 
 #define HFS_BNODE_LOCK		0

fs/isofs/rock.h

···
 	__u8 len_des;
 	__u8 len_src;
 	__u8 ext_ver;
-	__u8 data[0];
+	__u8 data[];
 } __attribute__ ((packed));
 
 struct RR_RR_s {
···
 struct SL_component {
 	__u8 flags;
 	__u8 len;
-	__u8 text[0];
+	__u8 text[];
 } __attribute__ ((packed));
 
 struct RR_SL_s {
···
 
 struct RR_NM_s {
 	__u8 flags;
-	char name[0];
+	char name[];
 } __attribute__ ((packed));
 
 struct RR_CL_s {
···
 
 struct RR_TF_s {
 	__u8 flags;
-	struct stamp times[0];	/* Variable number of these beasts */
+	struct stamp times[];	/* Variable number of these beasts */
 } __attribute__ ((packed));
 
 /* Linux-specific extension for transparent decompression */

fs/select.c

···
 struct poll_table_page {
 	struct poll_table_page * next;
 	struct poll_table_entry * entry;
-	struct poll_table_entry entries[0];
+	struct poll_table_entry entries[];
 };
 
 #define POLL_TABLE_FULL(table) \
···
 struct poll_list {
 	struct poll_list *next;
 	int len;
-	struct pollfd entries[0];
+	struct pollfd entries[];
 };
 
 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))

include/linux/fs.h

···
  */
 struct simple_transaction_argresp {
 	ssize_t size;
-	char data[0];
+	char data[];
 };
 
 #define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))