usb: gadget: configfs: Fix missing spin_lock_init()

usb: gadget: configfs: Fix missing spin_lock_init()

The driver allocates the spinlock but not initialize it.
Use spin_lock_init() on it to initialize it correctly.

This is detected by Coccinelle semantic patch.

Fixes: 1a1c851bbd70 ("usb: gadget: configfs: fix concurrent issue between composite APIs")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/r/20191030034046.188808-1-weiyongjun1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>