usb: dwc3: remove dwc3 dependency on host AND gadget.

DWC3 controller curretly depends on USB && USB_GADGET.
Some hardware may like to use only host feature on dwc3,
or only gadget feature.

So, removing this dependency of USB_DWC3 on USB and USB_GADGET.
Adding the mode of operaiton of DWC3 also here
HOST/GADGET/DUAL_ROLE based on which features are enabled.

[ balbi@ti.com :
	. make sure we have default modes for all possible Kernel
		configurations.
	. Remove the config -> menuconfig change as it's unnecessary
	. switch over to IS_ENABLED() ]

CC: Doug Anderson <dianders@chromium.org>
Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/debugfs.c

@@ -661,6 +661,7 @@ int dwc3_debugfs_init(struct dwc3 *dwc)
 		goto err1;
 	}
 
+#if IS_ENABLED(CONFIG_USB_DWC3_GADGET)
 	file = debugfs_create_file("mode", S_IRUGO | S_IWUSR, root,
 			dwc, &dwc3_mode_fops);
 	if (!file) {
@@ -681,6 +682,7 @@ int dwc3_debugfs_init(struct dwc3 *dwc)
 		ret = -ENOMEM;
 		goto err1;
 	}
+#endif
 
 	return 0;