USB: mos7840: remove redundant condition

This patch removes redundant condition.

 (length && length > 5) can be reduced to a single evaluation.

Tested by compilation only.
Caught by cppcheck.
Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/mos7840.c

@@ -635,7 +635,7 @@ static void mos7840_interrupt_callback(struct urb *urb)
 	 * Byte 4 IIR Port 4 (port.number is 3)
 	 * Byte 5 FIFO status for both */
 
-	if (length && length > 5) {
+	if (length > 5) {
 		dev_dbg(&urb->dev->dev, "%s", "Wrong data !!!\n");
 		return;
 	}