dwc3: use dwc3_host_init() and dwc3_host_exit() APIs

xhci->dev platform device properties are not retained as platform device
is added/removed w/o explicitly adding properties from start_host API.
Use dwc3_host_init() and dwc3_host_exit() APIs instead which will
explicitly add properties before adding the platform device.

Change-Id: Ieda9b7502ecf841f3a06291187fae59eeafca6ea
Signed-off-by: Mayank Rana <mrana@codeaurora.org>