usb: dwc3: msm: Remove struct dwc3_ext_xceiv

Remove this structure and move ID and VBUS state variables to
struct dwc3_msm. Also the callback functions can be eliminated
as dwc3_ext_event_notify() and dwc3_msm_block_reset() can be
called directly.

Change-Id: Idafa62480e54e383452fa9da193238178d6f0059
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>