usb: dwc3: msm: Remove charger from dwc3_otg

The charger detection structure is already embedded in struct
dwc3_msm, so use that and remove the pointer in dwc3_otg. Call
dwc3_start_chg_det() directly which eliminates the callbacks.

Change-Id: I42d6d7422ccded0055de6c94793295c948ddc404
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>