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>
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index f02b3e0..b417506 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -864,10 +864,24 @@
 void dwc3_set_mode(struct dwc3 *dwc, u32 mode);
 int dwc3_gadget_resize_tx_fifos(struct dwc3 *dwc);
 
+#if IS_ENABLED(CONFIG_USB_DWC3_HOST) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
 int dwc3_host_init(struct dwc3 *dwc);
 void dwc3_host_exit(struct dwc3 *dwc);
+#else
+static inline int dwc3_host_init(struct dwc3 *dwc)
+{ return 0; }
+static inline void dwc3_host_exit(struct dwc3 *dwc)
+{ }
+#endif
 
+#if IS_ENABLED(CONFIG_USB_DWC3_GADGET) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
 int dwc3_gadget_init(struct dwc3 *dwc);
 void dwc3_gadget_exit(struct dwc3 *dwc);
+#else
+static inline int dwc3_gadget_init(struct dwc3 *dwc)
+{ return 0; }
+static inline void dwc3_gadget_exit(struct dwc3 *dwc)
+{ }
+#endif
 
 #endif /* __DRIVERS_USB_DWC3_CORE_H */