vhost: fix missing device checks
virtio-net search for it's device in reset_owner.
The function don't check the return result of get_config_ll_entry.
Using get_config_ll_entry in reset_owner don't show any error when the
device is not found. This patch fix this by using get_device instead
instead of get_config_ll_entry.
In user_get_vring_base, get_device return is not checked and may cause
segfault when device is not found.
Signed-off-by: Jerome Jutteau <jerome.jutteau@outscale.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>