HID: hidraw: Replace Confusing += Operator with =

Setting of the return value of hidraw_read() uses the += operator when
= is more appropriate.  There is no case where ret can be anything
other than zero when the assignment is made, making = equivalent to
+= and much more clear.
Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hidraw.c

@@ -91,7 +91,7 @@ static ssize_t hidraw_read(struct file *file, char __user *buffer, size_t count,
 			ret = -EFAULT;
 			goto out;
 		}
-		ret += len;
+		ret = len;
 
 		kfree(list->buffer[list->tail].value);
 		list->tail = (list->tail + 1) & (HIDRAW_BUFFER_SIZE - 1);