UPSTREAM: vsock/virtio: non-linear skb handling for tap

For tap device new skb is created and data from the current skb is
copied to it. This adds copying data from non-linear skb to new
the skb.

Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
(cherry picked from commit 4b0bf10e)
Bug: 421244320
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I7f184148aa8a91032c65ef61326ca7f513f157a3