usb: phy: make it a menuconfig

We already have a considerable amount of USB
PHY drivers, making it a menuconfig just
prevents us from adding too much churn to
USB's menuconfig.

While at that, also select USB_OTG_UTILS from
this new menuconfig just to keep backwards
compatibility until we manage to remove
that symbol.

Signed-off-by: Felipe Balbi <balbi@ti.com>

include/linux/usb/phy.h

@@ -161,7 +161,7 @@ usb_phy_shutdown(struct usb_phy *x)
 }
 
 /* for usb host and peripheral controller drivers */
-#ifdef CONFIG_USB_OTG_UTILS
+#if IS_ENABLED(CONFIG_USB_PHY)
 extern struct usb_phy *usb_get_phy(enum usb_phy_type type);
 extern struct usb_phy *devm_usb_get_phy(struct device *dev,
 	enum usb_phy_type type);