Add support for sysfs to the IPMI device interface.

Clean-ups based on Dimitry Torokovs comment by Philipp Hahn.
Signed-off-by: NCorey Minyard <minyard@acm.org>
Signed-off-by: NPhilipp Hahn <pmhahn@titan.lahn.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>