vhost_net: Rename vhost_set_vring_enable() for clarity

vhost_net: Rename vhost_set_vring_enable() for clarity

This is a cosmetic change with no functional impact.

The function vhost_set_vring_enable() is specific to vhost_net and
is used outside of vhost_net.c (specifically, in
hw/net/virtio-net.c). To prevent confusion with other similarly named
vhost functions, such as the one found in cryptodev-vhost.c, it has
been renamed to vhost_net_set_vring_enable(). This clarifies that the
function belongs to the vhost_net module.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>