usb: misc: Fixed assignment error in if statement

Fixed the assignment error in an if statement in adutux.c

Signed-off-by: Lisa Nguyen <lisa@xenapiadmin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
index 267b194..eb3c8c1 100644
--- a/drivers/usb/misc/adutux.c
+++ b/drivers/usb/misc/adutux.c
@@ -276,7 +276,8 @@
 
 	subminor = iminor(inode);
 
-	if ((retval = mutex_lock_interruptible(&adutux_mutex))) {
+	retval = mutex_lock_interruptible(&adutux_mutex);
+	if (retval) {
 		dbg(2, "%s : mutex lock failed", __func__);
 		goto exit_no_lock;
 	}