ipmi: support I/O resources in OF driver

The current OF probing assumes that the resource is IORESOURCE_MEM.  This
checks for the IORESOURCE_IO flag and behaves appropriately.  An I/O resource
can exist with an ipmi device node on a legacy ISA bus.

Signed-off-by: Nate Case <ncase@xes-inc.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>