ipmi/watchdog: fix wdog hang on panic waiting for ipmi response

Commit c49c0976 ("ipmi: Don't call receive handler in the
panic context") means that the panic_recv_free is not called during a
panic and the atomic count does not drop to 0.

Fix this by only expecting one decrement of the atomic variable
which comes from panic_smi_free.

Signed-off-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>