usb: usbip: Use DEFINE_SPINLOCK() for spinlock

spinlock can be initialized automatically with DEFINE_SPINLOCK()
rather than explicitly calling spin_lock_init().

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Link: https://lore.kernel.org/r/20201223141431.835-1-zhengyongjun3@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>