Staging: hv: vmbus: Change the memory barrier in hv_ringbuffer_write()

Use the correct memory barrier interface in Change the memory barrier
in hv_ringbuffer_write().

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Abhishek Kane <v-abkane@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>