iwlegacy: 4965-calib: Demote seemingly accidental kernel-doc header

iwlegacy: 4965-calib: Demote seemingly accidental kernel-doc header

No parameters were documented and it's the only one in the file.

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

 drivers/net/wireless/intel/iwlegacy/4965-calib.c:608: warning: Function parameter or member 'il' not described in 'il4965_find_disconn_antenna'
 drivers/net/wireless/intel/iwlegacy/4965-calib.c:608: warning: Function parameter or member 'average_sig' not described in 'il4965_find_disconn_antenna'
 drivers/net/wireless/intel/iwlegacy/4965-calib.c:608: warning: Function parameter or member 'data' not described in 'il4965_find_disconn_antenna'

Cc: Stanislaw Gruszka <stf_xl@wp.pl>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Linux Wireless <ilw@linux.intel.com>
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/20200821071644.109970-24-lee.jones@linaro.org