libertas_tf: Demote non-conformant kernel-doc headers

libertas_tf: Demote non-conformant kernel-doc headers

There are only 2 kernel-doc headers in this file and both are
incorrect.  The first one does not attempt to document the function at
all and the second one is suffering from severe doc-rot; the format is
wrong and only 1 out of 3 parameters are being documented.

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

 drivers/net/wireless/marvell/libertas_tf/main.c:129: warning: Function parameter or member 't' not described in 'command_timer_fn'
 drivers/net/wireless/marvell/libertas_tf/main.c:554: warning: Function parameter or member 'card' not described in 'lbtf_add_card'
 drivers/net/wireless/marvell/libertas_tf/main.c:554: warning: Function parameter or member 'dmdev' not described in 'lbtf_add_card'
 drivers/net/wireless/marvell/libertas_tf/main.c:554: warning: Function parameter or member 'ops' not described in 'lbtf_add_card'

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/20200819072402.3085022-5-lee.jones@linaro.org