staging: ath6kl: update TODO file / maintainers

This updates the TODO file to reflect new changes on development.

Cc: Joe Perches <joe@perches.com>
Cc: Naveen Singh <nsingh@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>