vhost-user: Adopt new backend naming

The Vhost-user specification changed feature and request
naming from _SLAVE_ to _BACKEND_.

This patch adopts the new naming convention.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Message-Id: <20230208203259.381326-4-maxime.coquelin@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2 files changed