Move ath_dfs_pool_stats to dfs_pattern_detector
code to be not specyfic only for ath9k.
Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com> Reviewed-by: Luis R. Rodriguez <mcgrof@do-not-panic.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>