atmel: Demote non-kerneldoc header to standard comment block

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

 drivers/net/wireless/atmel/atmel.c:4232: warning: Cannot understand     This file is part of net.russotto.AtmelMACFW, hereto referred to

Cc: Simon Kelley <simon@thekelleys.org.uk>
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/20200814113933.1903438-6-lee.jones@linaro.org