Revert "virtio/vsock: don't drop skbuff on copy failure"

This reverts commit 1e5f00e9 which is
commit 8daaf39f upstream.

It needs to be reverted, as the function virtio_transport_free_pkt() is
in the stable Android ABI, and this function is removed in the 6.1.63
kernel as part of a series of fixes and optimizations of the virtio
networking connection.  To preserve the ABI (and thereby keeping the
slower interface), revert the commit for now.

If this needs to come back in the future, if performance for this
interface needs to be resolved, it can be done so in an ABI-safe way.

Bug: 161946584
Change-Id: Ie929bb2fbb4e3dc3cadc1e0d3b63ed8e83257a4a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>