power: smb-lib: Add USB notification

In designs without the pd-phy interface the usb
insertion/removal and CC_orientation needs to be
notified to the usb stack by the charger driver.
Add this notification support via the extcon interface.

CRs-Fixed: 2086422
Change-Id: I22eae3f818859c8fbd08066f690517d4210c7dd3
Signed-off-by: Ankit Sharma <ansharma@codeaurora.org>