ipmi: Make the smi watcher be disabled immediately when not needed

commit e1891cffd4c4896a899337a243273f0e23c028df upstream.

The code to tell the lower layer to enable or disable watching for
certain things was lazy in disabling, it waited until a timer tick
to see if a disable was necessary.  Not a really big deal, but it
could be improved.

Modify the code to enable and disable watching immediately and don't
do it from the background timer any more.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Kamlakant Patel <kamlakant.patel@cavium.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>