ath: dfs_pri_detector: Demote zero/half completed kernel-doc headers

ath: dfs_pri_detector: Demote zero/half completed kernel-doc headers

There are only a couple of these and none of them are conformant.

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/ath/dfs_pri_detector.c:39: warning: Function parameter or member 'head' not described in 'pulse_elem'
 drivers/net/wireless/ath/dfs_pri_detector.c:46: warning: Function parameter or member 'val' not described in 'pde_get_multiple'
 drivers/net/wireless/ath/dfs_pri_detector.c:46: warning: Function parameter or member 'fraction' not described in 'pde_get_multiple'
 drivers/net/wireless/ath/dfs_pri_detector.c:46: warning: Function parameter or member 'tolerance' not described in 'pde_get_multiple'

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201102112410.1049272-23-lee.jones@linaro.org