If the return value of vhci_init_attr_group and
sysfs_create_group is non-zero, which mean they failed
to init attr_group and create sysfs group, so it would
better add 'failed' message to indicate that.
This patch also change pr_err to dev_err to trace which
device is failed.

Fixes: 0775a9cb ("usbip: vhci extension: modifications to vhci driver")
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190916150921.152977-1-maowenan@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>