iwlwifi: Fix frequency in rx_status fill

This patch fixes a bug in RX path, the frequency was wrongly set in the
ieee80211_rx_status. This bug led to an empty scan list in A band.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>