mwifiex: usb: 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].

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

This issue was found with the help of Coccinelle and audited and fixed,
manually.

[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/109Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210809211134.GA22488@embeddedor

drivers/net/wireless/marvell/mwifiex/usb.h

@@ -134,7 +134,7 @@ struct fw_sync_header {
 struct fw_data {
 	struct fw_header fw_hdr;
 	__le32 seq_num;
-	u8 data[1];
+	u8 data[];
 } __packed;
 
 #endif /*_MWIFIEX_USB_H */