We hit the problem with below sequence:
- ci_udc_vbus_session() update vbus_active flag and ci->driver
is valid,
- before calling the ci_hdrc_gadget_connect(),
usb_gadget_udc_stop() is called by application remove gadget
driver,
- ci_udc_vbus_session() will contine do ci_hdrc_gadget_connect() as
gadget_ready is 1, so udc interrupt is enabled, but ci->driver is
NULL.
- USB connection irq generated but ci->driver is NULL.

As udc irq only should be enabled when gadget driver is binded, so
add spinlock to protect the usb irq enable for vbus session handling.
Signed-off-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>