usb: it82xx2: fix issue with the unexpected setting of the ready bit

In the IT82xx2 chip, the ready bit is automatically cleared by
hardware. When setting other bits, there is a chance that the ready bit
hasn't been cleared yet, leading to unexpected USB transactions. This
change ensures that the ready bit is always set to '0' when setting the
endpoint control value.

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