usb: it82xx2: lock irq for handling suspended flag

The suspended flag is checked during SOF and RESUME interrupts, and it
is modified within a delayable work item. To prevent race conditions,
this update ensures that interrupts are disabled (locking IRQs) before
modifying the suspended flag. Additionally, the RESUME interrupt is
enabled only when the USB is suspended.

Signed-off-by: Ren Chen <Ren.Chen@ite.com.tw>