USB: usbmon: remove assignment from IS_ERR argument

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2;
statement S1,S2;
@@

+e1 = e2;
if (IS_ERR(
    e1
-   = e2
   )) S1 else S2
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/mon/mon_text.c

@@ -387,7 +387,8 @@ static ssize_t mon_text_read_t(struct file *file, char __user *buf,
 	struct mon_event_text *ep;
 	struct mon_text_ptr ptr;
 
-	if (IS_ERR(ep = mon_text_read_wait(rp, file)))
+	ep = mon_text_read_wait(rp, file);
+	if (IS_ERR(ep))
 		return PTR_ERR(ep);
 	mutex_lock(&rp->printf_lock);
 	ptr.cnt = 0;
@@ -414,7 +415,8 @@ static ssize_t mon_text_read_u(struct file *file, char __user *buf,
 	struct mon_event_text *ep;
 	struct mon_text_ptr ptr;
 
-	if (IS_ERR(ep = mon_text_read_wait(rp, file)))
+	ep = mon_text_read_wait(rp, file);
+	if (IS_ERR(ep))
 		return PTR_ERR(ep);
 	mutex_lock(&rp->printf_lock);
 	ptr.cnt = 0;