NTB: EPF: fix possible memory leak in pci_vntb_probe()

As ntb_register_device() don't handle error of device_register(),
if ntb_register_device() returns error in pci_vntb_probe(), name of kobject
which is allocated in dev_set_name() called in device_add() is leaked.

As comment of device_add() says, it should call put_device() to drop the
reference count that was set in device_initialize()
when it fails, so the name can be freed in kobject_cleanup().

Signed-off-by: ruanjinjie <ruanjinjie@huawei.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>