tty: ipwireless: remove unused ipw_dev::attribute_memory

clang-struct [1] found ipw_dev::attribute_memory unused.

As far as I can see it was never used since the driver merge. Drop it.

[1] https://github.com/jirislaby/clang-struct

Signed-off-by: "Jiri Slaby (SUSE)" <[e-mail]>
Cc: Jiri Kosina <[e-mail]>
Cc: David Sterba <[e-mail]>
Acked-by: David Sterba <[e-mail]>
Acked-by: Jiri Kosina <[e-mail]>
Reviewed-by: Ilpo Järvinen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/ipwireless/main.h

···
 
 	void __iomem *common_memory;
 
-	/* Reference to attribute memory, containing CIS data */
-	void *attribute_memory;
-
 	/* Hardware context */
 	struct ipw_hardware *hardware;
 	/* Network layer context */