staging: comedi: fix typo

Fix spelling mistake: "lenghth" -> "length"

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/usbduxfast.c

@@ -61,7 +61,7 @@
 #define USBDUXFASTSUB_CPUCS	0xE600
 
 /*
- * max lenghth of the transfer-buffer for software upload
+ * max length of the transfer-buffer for software upload
  */
 #define TB_LEN	0x2000