b43: Change schedule for old-fw support removal

The scheduled date for the removal of old fw support was in July 2008.
However, we're not going to remove the support unless it causes a major
headache. So change the schedule from "July 2008" to "when it causes headaches".

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>