ipmi:watchdog: Set panic count to proper value on a panic

You will get two decrements when the messages on a panic are sent, not
one, since commit 2033f685 ("ipmi: Free receive messages when in an
oops") was added, but the watchdog code had a bug where it didn't set
the value properly.
Reported-by: Anton Lundin <glance@acc.umu.se>
Cc: <Stable@vger.kernel.org> # v5.4+
Fixes: 2033f685 ("ipmi: Free receive messages when in an oops")
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_watchdog.c

@@ -497,7 +497,7 @@ static void panic_halt_ipmi_heartbeat(void)
 	msg.cmd = IPMI_WDOG_RESET_TIMER;
 	msg.data = NULL;
 	msg.data_len = 0;
-	atomic_inc(&panic_done_count);
+	atomic_add(2, &panic_done_count);
 	rv = ipmi_request_supply_msgs(watchdog_user,
 				      (struct ipmi_addr *) &addr,
 				      0,
@@ -507,7 +507,7 @@ static void panic_halt_ipmi_heartbeat(void)
 				      &panic_halt_heartbeat_recv_msg,
 				      1);
 	if (rv)
-		atomic_dec(&panic_done_count);
+		atomic_sub(2, &panic_done_count);
 }
 
 static struct ipmi_smi_msg panic_halt_smi_msg = {
@@ -531,12 +531,12 @@ static void panic_halt_ipmi_set_timeout(void)
 	/* Wait for the messages to be free. */
 	while (atomic_read(&panic_done_count) != 0)
 		ipmi_poll_interface(watchdog_user);
-	atomic_inc(&panic_done_count);
+	atomic_add(2, &panic_done_count);
 	rv = __ipmi_set_timeout(&panic_halt_smi_msg,
 				&panic_halt_recv_msg,
 				&send_heartbeat_now);
 	if (rv) {
-		atomic_dec(&panic_done_count);
+		atomic_sub(2, &panic_done_count);
 		pr_warn("Unable to extend the watchdog timeout\n");
 	} else {
 		if (send_heartbeat_now)