iwlagn: move iwl_process_scan_complete up

To make the next patch easier to read, move
the function up, it'll be needed earlier in
this file in the next patch.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>