[PATCH] Add sysfs support for the IPMI device interface

Add support for sysfs to the IPMI device interface.

Clean-ups based on Dimitry Torokovs comment by Philipp Hahn.

Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Philipp Hahn <pmhahn@titan.lahn.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>