usb: dwc2: Add call_gadget() function call

Added call_gadget() function call when entering to L1 state
to inform gadget that core is in L1 state.

Did the same thing when exiting from L1 state
to inform gadget that core is in L0 state.

Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>