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

drivers/net/wireless/ath/dfs_pri_detector.c

@@ -29,18 +29,17 @@ struct ath_dfs_pool_stats global_dfs_pool_stats = {};
 	(MIN + PRI_TOLERANCE == MAX - PRI_TOLERANCE ? \
 	MIN + PRI_TOLERANCE : RUNTIME)
 
-/**
+/*
  * struct pulse_elem - elements in pulse queue
- * @ts: time stamp in usecs
  */
 struct pulse_elem {
 	struct list_head head;
 	u64 ts;
 };
 
-/**
+/*
  * pde_get_multiple() - get number of multiples considering a given tolerance
- * @return factor if abs(val - factor*fraction) <= tolerance, 0 otherwise
+ * Return value: factor if abs(val - factor*fraction) <= tolerance, 0 otherwise
  */
 static u32 pde_get_multiple(u32 val, u32 fraction, u32 tolerance)
 {
@@ -70,7 +69,7 @@ static u32 pde_get_multiple(u32 val, u32 fraction, u32 tolerance)
 	return factor;
 }
 
-/**
+/*
  * DOC: Singleton Pulse and Sequence Pools
  *
  * Instances of pri_sequence and pulse_elem are kept in singleton pools to