net: ethernet: ti: am65-cpts: Document am65_cpts_rx_enable()'s 'en' parameter

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

 drivers/net/ethernet/ti/am65-cpts.c:736: warning: Function parameter or member 'en' not described in 'am65_cpts_rx_enable'
 drivers/net/ethernet/ti/am65-cpts.c:736: warning: Excess function parameter 'skb' description in 'am65_cpts_rx_enable'
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ti/am65-cpts.c

@@ -727,7 +727,7 @@ static long am65_cpts_ts_work(struct ptp_clock_info *ptp)
 /**
  * am65_cpts_rx_enable - enable rx timestamping
  * @cpts: cpts handle
- * @skb: packet
+ * @en: enable
  *
  * This functions enables rx packets timestamping. The CPTS can timestamp all
  * rx packets.