Replace mentions of "list_struct" to "list_head"

There's no such thing as "list_struct".

Signed-off-by: Andrey Utkin <andrey.krieger.utkin@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/media/pci/cx18/cx18-driver.h

@@ -290,7 +290,7 @@ struct cx18_options {
  * list_entry_is_past_end - check if a previous loop cursor is off list end
  * @pos:	the type * previously used as a loop cursor.
  * @head:	the head for your list.
- * @member:	the name of the list_struct within the struct.
+ * @member:	the name of the list_head within the struct.
  *
  * Check if the entry's list_head is the head of the list, thus it's not a
  * real entry but was the loop cursor that walked past the end