Tweak /proc/ipmi removal

Driver does
	proc_mkdir("ipmi", NULL);
but
	remove_proc_entry(proc_ipmi_root->name, &proc_root);

This is OK and working if only slightly inconsistent.  Also changing
proc_root to NULL will help OpenVZ which has multiple proc roots and, as we
now know, requires matching parents in such cases.
Signed-off-by: NAlexey Dobriyan <adobriyan@sw.ru>
Cc: Corey Minyard <minyard@acm.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/ipmi/ipmi_msghandler.c

@@ -4136,7 +4136,7 @@ static __exit void cleanup_ipmi(void)
 	del_timer_sync(&ipmi_timer);
 
 #ifdef CONFIG_PROC_FS
-	remove_proc_entry(proc_ipmi_root->name, &proc_root);
+	remove_proc_entry(proc_ipmi_root->name, NULL);
 #endif /* CONFIG_PROC_FS */
 
 	driver_unregister(&ipmidriver);