usb: remove redundant D0 power state set

Pci_enable_device() will set device power state to D0,
so it's no need to do it again after call pci_enable_device().

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>