tegra: usb: set USB_PORTS_MAX to correct value

Both Tegra20 and Tegra30 have a max of 3 USB controllers.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/cpu/armv7/tegra20/usb.c

@@ -44,7 +44,7 @@
 #endif
 
 enum {
-	USB_PORTS_MAX	= 4,			/* Maximum ports we allow */
+	USB_PORTS_MAX	= 3,		/* Maximum ports we allow */
 };
 
 /* Parameters we need for USB */