linux-phytec-fsl

virtio: include asm/barrier explicitly

virtio_ring.h uses mb() and friends, make
it pull in asm/barrier.h itself, not rely
on other headers to do it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>