ipw2x00: age scan results on resume

Scanned BSS entries are timestamped with jiffies, which doesn't
increment across suspend and hibernate.  On resume, every BSS in the
scan list looks like it was scanned within the last 10 seconds,
irregardless of how long the machine was actually asleep.  Age scan
results on resume with the time spent during sleep so userspace has a
clue how old they really are.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>