ipmi: Check the BT interrupt enable periodically

On a reset, the BMC may reset the BT enable in the processor
registers (different than the global enables in the BMC).  Check
it periodically and fix it if necessary.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Tony Rex <tony.rex@ericsson.com>
Tested-by: Magnus Johansson E <magnus.e.johansson@ericsson.com>