iwlwifi: allow association on radar channel in power save

This patch disables power save upon association and enables it back
after association. This allows to associate to AP on a radar channel
if power save is enabled.

Radar and passive channels are not allowed for TX (required for association)
unless RX is received but PS may close the radio and no RX will be received
effectively failing association.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>