USB: assign instead of equal in usbtmc.c

Assign operator instead of equality test in the usbtmc_ioctl_abort_bulk_in() function.
Signed-off-by: Maxim A. Nikulin <M.A.Nikulin@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/usbtmc.c

@@ -268,7 +268,7 @@ static int usbtmc_ioctl_abort_bulk_in(struct usbtmc_device_data *data)
 				dev_err(dev, "usb_bulk_msg returned %d\n", rv);
 				goto exit;
 			}
-		} while ((actual = max_size) &&
+		} while ((actual == max_size) &&
 			 (n < USBTMC_MAX_READS_TO_CLEAR_BULK_IN));
 
 	if (actual == max_size) {