module: do percpu allocation after uniqueness check. No, really!

commit 8d8022e8aba85192e937f1f0f7450e256d66ae5c upstream.

v3.8-rc1-5-g1fb9341 was supposed to stop parallel kvm loads exhausting
percpu memory on large machines:

    Now we have a new state MODULE_STATE_UNFORMED, we can insert the
    module into the list (and thus guarantee its uniqueness) before we
    allocate the per-cpu region.

In my defence, it didn't actually say the patch did this.  Just that
we "can".

This patch actually *does* it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Jim Hull <jim.hull@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>