usb: phy: am335x-control: make it compile with

Randy reported this
|drivers/usb/phy/phy-am335x-control.c:45:3: error: implicit declaration
|of function '__WARN' [-Werror=implicit-function-declaration]

and left it as an excercice to figure out that this happens only with
CONFIG_BUG=n. As a fix I replace it with WARN_ON(). And there is a space
before return so fix this, too.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/phy/phy-am335x-control.c

@@ -42,8 +42,8 @@ static void am335x_phy_power(struct phy_control *phy_ctrl, u32 id, bool on)
 		reg = AM335X_USB1_CTRL;
 		break;
 	default:
-		__WARN();
-		 return;
+		WARN_ON(1);
+		return;
 	}
 
 	val = readl(usb_ctrl->phy_reg + reg);