USB: testusb: add path /dev/bus/usb to default search paths for usbfs

As real device-nodes managed by udev whose nodes lived in /dev/bus/usb
are mostly used today, let testusb tool use that directory as one default
path make tool be more convenient to use.

Signed-off-by: Du Changbin <changbinx.du@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/usb/testusb.c

@@ -358,6 +358,7 @@ static const char *usbfs_dir_find(void)
 {
 	static char usbfs_path_0[] = "/dev/usb/devices";
 	static char usbfs_path_1[] = "/proc/bus/usb/devices";
+	static char udev_usb_path[] = "/dev/bus/usb";
 
 	static char *const usbfs_paths[] = {
 		usbfs_path_0, usbfs_path_1
@@ -376,6 +377,10 @@ static const char *usbfs_dir_find(void)
 		}
 	} while (++it != end);
 
+	/* real device-nodes managed by udev */
+	if (access(udev_usb_path, F_OK) == 0)
+		return udev_usb_path;
+
 	return NULL;
 }