The previous patch made sparse warn about percpu variables being used
directly without going through percpu accessors.  This patch
implements the other half - checking whether non percpu variable is
passed into percpu accessors.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>