carl9170: devres ar->survey_info

driver keeps the same survey_info struct for its lifetime around.
This is used because while firmware does help by providing accounting
information of the current channel, it doesn't keep track on the
remaining channels.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/9b9a059b384f49587f4384ba47f01d3fb2115b22.1646250537.git.chunkeey@gmail.com