USB: accept RNDIS configs if there's no alternative

This patch (as1410) makes a slight change to the strategy used for
choosing a default configuration.  Currently we skip configs whose
first interface is RNDIS, if the kernel wasn't built with the
corresponding driver.  This risks losing access to the other
interfaces in those configs.  In addition, if there is only one config
then we will end up not configuring the device at all.

This changes the logic; now such configurations will be skipped only
if there is at least one other config.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Adam Kropelin <akropel1@rochester.rr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/generic.c

@@ -105,8 +105,10 @@ int usb_choose_configuration(struct usb_device *udev)
 		/* When the first config's first interface is one of Microsoft's
 		 * pet nonstandard Ethernet-over-USB protocols, ignore it unless
 		 * this kernel has enabled the necessary host side driver.
+		 * But: Don't ignore it if it's the only config.
 		 */
-		if (i == 0 && desc && (is_rndis(desc) || is_activesync(desc))) {
+		if (i == 0 && num_configs > 1 && desc &&
+				(is_rndis(desc) || is_activesync(desc))) {
 #if !defined(CONFIG_USB_NET_RNDIS_HOST) && !defined(CONFIG_USB_NET_RNDIS_HOST_MODULE)
 			continue;
 #else