ipmi: add powerpc openfirmware sensing

ipmi: add powerpc openfirmware sensing

Add support for of_platform_driver to the ipmi_si module.  When loading the
module, the driver will be registered to of_platform.  The driver will be
probed for all devices with the type ipmi.  It's supporting devices with
compatible settings ipmi-kcs, ipmi-smic and ipmi-bt.  Only ipmi-kcs could be
tested.

Signed-off-by: Christian Krafft <[email protected]>
Acked-by: Heiko J Schick <[email protected]>
Signed-off-by: Corey Minyard <[email protected]>
Acked-by: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>