ipmi: add pci remove handling

Add pci_remove handling to the driver, so it will clean up if
the device is hot-removed.

Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>