ath5k: Fix kerneldoc formatting issue

Kerneldoc expects attributes/parameters to be in '@*.: ' format and
gets confused if the variable does not follow the type/attribute
definitions.

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

 drivers/net/wireless/ath/ath5k/base.c:1111: warning: Function parameter or member 'ah' not described in 'ath5k_drain_tx_buffs'

Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Nick Kossifidis <mickflemm@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: "Luis R. Rodriguez" <mcgrof@winlab.rutgers.edu>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: bpf@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/20200814113933.1903438-21-lee.jones@linaro.org