[PATCH] ipmi: use rcu lock for using command receivers

Use rcu_read_lock for the cmd_rcvrs list, since that was what what
intended, anyway.  This means that all the users of the cmd_rcvrs_lock are
tasks, so the irq disables are no longer required for that lock and it can
become a semaphore.

Signed-off-by: Corey Minyard <minyard@acm.org>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>