wil6210: fix length check in __wmi_send

The current length check:
sizeof(cmd) + len > r->entry_size
will allow very large values of len (> U16_MAX - sizeof(cmd))
and can cause a buffer overflow. Fix the check to cover this case.
In addition, ensure the mailbox entry_size is not too small,
since this can also bypass the above check.

Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/wil6210/wmi.c

@@ -448,7 +448,7 @@ static int __wmi_send(struct wil6210_priv *wil, u16 cmdid, void *buf, u16 len)
 	uint retry;
 	int rc = 0;
 
-	if (sizeof(cmd) + len > r->entry_size) {
+	if (len > r->entry_size - sizeof(cmd)) {
 		wil_err(wil, "WMI size too large: %d bytes, max is %d\n",
 			(int)(sizeof(cmd) + len), r->entry_size);
 		return -ERANGE;