Firstly a rename, then a split (there are 2 'len's that need documenting).

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

 drivers/net/wireless/ti/wlcore/cmd.c:832: warning: Function parameter or member 'buf_len' not described in 'wl1271_cmd_test'
 drivers/net/wireless/ti/wlcore/cmd.c:832: warning: Excess function parameter 'len' description in 'wl1271_cmd_test'
 drivers/net/wireless/ti/wlcore/cmd.c:862: warning: Function parameter or member 'cmd_len' not described in 'wl1271_cmd_interrogate'
 drivers/net/wireless/ti/wlcore/cmd.c:862: warning: Function parameter or member 'res_len' not described in 'wl1271_cmd_interrogate'
 drivers/net/wireless/ti/wlcore/cmd.c:862: warning: Excess function parameter 'len' description in 'wl1271_cmd_interrogate'

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Hari Nagalla <hnagalla@gmail.com>
Cc: Guy Mishol <guym@ti.com>
Cc: Maital Hahn <maitalm@ti.com>
Cc: Luciano Coelho <luciano.coelho@nokia.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/20200819072402.3085022-7-lee.jones@linaro.org