[PATCH] ipmi poweroff: fix chassis control

The IPMI power control function proc_write_chassctrl was badly written, it
directly used userspace pointers, it assumed that strings were NULL
terminated, and it used the evil sscanf function.  This converts over to
using the sysctl interface for this data and changes the semantics to be a
little more logical.

Signed-off-by: Corey Minyard <minyard@acm.org>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>