fix typos "wich" -> "which"

Signed-off-by: Uwe Zeisberger <zeisberg@informatik.uni-freiburg.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index a8455c9..495db57 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -102,7 +102,7 @@
 	.no_dynamic_id = 	1,
 };
 
-/* The card has three separate interfaces, wich the serial driver
+/* The card has three separate interfaces, which the serial driver
  * recognizes separately, thus num_port=1.
  */
 static struct usb_serial_driver option_3port_device = {