[PATCH] ipmi: fix return codes in failure case

These returns should be negative, like the others in this function.

Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>