wl3501_cs: Fix misspelling and provide missing documentation

wl3501_cs: Fix misspelling and provide missing documentation

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

 In file included from drivers/net/wireless/wl3501_cs.c:57:
 drivers/net/wireless/wl3501_cs.c:143: warning: Function parameter or member 'reg_domain' not described in 'iw_valid_channel'
 drivers/net/wireless/wl3501_cs.c:143: warning: Excess function parameter 'reg_comain' description in 'iw_valid_channel'
 drivers/net/wireless/wl3501_cs.c:469: warning: Function parameter or member 'data' not described in 'wl3501_send_pkt'
 drivers/net/wireless/wl3501_cs.c:469: warning: Function parameter or member 'len' not described in 'wl3501_send_pkt'

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Fox Chen <mhchen@golf.ccl.itri.org.tw>
Cc: de Melo <acme@conectiva.com.br>
Cc: Gustavo Niemeyer <niemeyer@conectiva.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/20201102112410.1049272-25-lee.jones@linaro.org