usb: dwc3-msm: Call client on usb connect/disconnect events

Add support to call vxr7200 driver's function when usb cable is connected
or disconnected.

Change-Id: I9662376fb70a276084027d384548c933f6b939df
Signed-off-by: Rajesh Bharathwaj <rajeshbharathwaj@codeaurora.org>