staging: hv: use sync_bitops when interacting with the hypervisor

staging: hv: use sync_bitops when interacting with the hypervisor

commit 22356585712d1ff08fbfed152edd8b386873b238 upstream.

Locking is required when tweaking bits located in a shared page, use the
sync_ version of bitops. Without this change vmbus_on_event() will miss
events and as a result, vmbus_isr() will not schedule the receive tasklet.

[Backported to 2.6.32 stable kernel by Haiyang Zhang <haiyangz@microsoft.com>]

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>