virtio: fix grammar in virtio_map_ops docs

virtio: fix grammar in virtio_map_ops docs

[ Upstream commit c15f42e09178d2849744ccf064200f5e7f71e688 ]

Fix grammar issues in the virtio_map_ops docs:
- missing article before "transport"
- "implements" -> "implement" to match subject

Fixes: bee8c7c24b73 ("virtio: introduce map ops in virtio core")
Message-Id: <3f7bcae5a984f14b72e67e82572b110acb06fa7e.1763026134.git.mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>