usb: dwc3: Disable host mode if operational mode is DRD (or OTG)

Host mode initialization is affecting peripheral mode also which
stops working after xhci initialization. Hence, disable it until
host issues are resolved to use DWC3 in peripheral mode.

Change-Id: Icfa63b873d7777f00e1dbc6048814e9cf71a2328
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>