Drivers: hv: balloon: don't wait for ol_waitevent when memhp_auto_online is enabled

Drivers: hv: balloon: don't wait for ol_waitevent when memhp_auto_online is enabled

BugLink: http://bugs.launchpad.net/bugs/1650059
With the recently introduced in-kernel memory onlining
(MEMORY_HOTPLUG_DEFAULT_ONLINE) these is no point in waiting for pages
to come online in the driver and we can get rid of the waiting.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit a132c54cbcb8c239a64370b9cd9468908398bc6e)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>