s390/3270: drop unused spinlock from struct con3270

I was checking why this spinlock was never initialized, but it turns
out it's not used anywhere, so we can drop it.

Signed-off-by: Jean Delvare <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/char/con3270.c

···
  */
 struct con3270 {
 	struct raw3270_view view;
-	spinlock_t lock;
 	struct list_head freemem;	/* list of free memory for strings. */
 
 	/* Output stuff. */