usb: gadget: f_cdev: Add remote wakeup capability from notify_serial_state

Currently if the Modem sends notifications like Rind Indicator
or Carrier Detect, we just bail out if USB is already suspended.
Add remote wakeup capability in this path.

Change-Id: I62321d67e54390f167776af563c0b666b0d9e789
Signed-off-by: Prashanth K <quic_prashk@quicinc.com>