scsi: message: fusion: Replace one-element 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].

Also, this helps with the ongoing efforts to enable -Warray-bounds by
fixing the following warning:

drivers/message/fusion/mptbase.c: In function ‘mptbase_reply’:
drivers/message/fusion/mptbase.c:7747:62: warning: array subscript 1 is above array bounds of ‘U32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds]
7747 | ioc->events[idx].data[ii] = le32_to_cpu(pEventReply->Data[ii]);
./include/uapi/linux/byteorder/little_endian.h:34:51: note: in definition of macro ‘__le32_to_cpu’
34 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
| ^
drivers/message/fusion/mptbase.c:7747:33: note: in expansion of macro ‘le32_to_cpu’
7747 | ioc->events[idx].data[ii] = le32_to_cpu(pEventReply->Data[ii]);
|

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Link: https://lore.kernel.org/r/20210324230036.GA67851@embeddedor
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/message/fusion/lsi/mpi_ioc.h

···
      U32                    IOCLogInfo;                 /* 10h */
      U32                    Event;                      /* 14h */
      U32                    EventContext;               /* 18h */
-     U32                    Data[1];                    /* 1Ch */
+     U32                    Data[];			/* 1Ch */
 } MSG_EVENT_NOTIFY_REPLY, MPI_POINTER PTR_MSG_EVENT_NOTIFY_REPLY,
   EventNotificationReply_t, MPI_POINTER pEventNotificationReply_t;