ipc/msg: replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct compat_msgbuf.

There are no binary differences after this conversion.

Link: KSPP/linux#79
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Thorsten Blum <[email protected]>
Cc: "Sun, Jiebin" <[email protected]>
Cc: Tim Chen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

ipc/msg.c

@@ -978,7 +978,7 @@ SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 
 struct compat_msgbuf {
 	compat_long_t mtype;
-	char mtext[1];
+	char mtext[];
 };
 
 long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp,