virtio-net: Fix vq->use_event_idx flag check

VIRTIO_RING_F_EVENT_IDX is a bit position value, but
virtio_init_device_vq populates vq->use_event_idx by ANDing this value
directly to vdev->features.

Fix the check for this flag in virtio_init_device_vq.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Tu Dinh Ngoc <dinhngoc.tu@irit.fr>
Link: https://lore.kernel.org/r/20220929121858.156-1-dinhngoc.tu@irit.fr


Signed-off-by: Will Deacon <will@kernel.org>