wil6210: pmc: Demote a few nonconformant kernel-doc function headers

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

 drivers/net/wireless/ath/wil6210/pmc.c:43: warning: Function parameter or member 'wil' not described in 'wil_pmc_alloc'
 drivers/net/wireless/ath/wil6210/pmc.c:43: warning: Function parameter or member 'num_descriptors' not described in 'wil_pmc_alloc'
 drivers/net/wireless/ath/wil6210/pmc.c:43: warning: Function parameter or member 'descriptor_size' not described in 'wil_pmc_alloc'
 drivers/net/wireless/ath/wil6210/pmc.c:229: warning: Function parameter or member 'wil' not described in 'wil_pmc_free'
 drivers/net/wireless/ath/wil6210/pmc.c:229: warning: Function parameter or member 'send_pmc_cmd' not described in 'wil_pmc_free'
 drivers/net/wireless/ath/wil6210/pmc.c:307: warning: Function parameter or member 'wil' not described in 'wil_pmc_last_cmd_status'
 drivers/net/wireless/ath/wil6210/pmc.c:320: warning: Function parameter or member 'filp' not described in 'wil_pmc_read'
 drivers/net/wireless/ath/wil6210/pmc.c:320: warning: Function parameter or member 'buf' not described in 'wil_pmc_read'
 drivers/net/wireless/ath/wil6210/pmc.c:320: warning: Function parameter or member 'count' not described in 'wil_pmc_read'
 drivers/net/wireless/ath/wil6210/pmc.c:320: warning: Function parameter or member 'f_pos' not described in 'wil_pmc_read'

Cc: Maya Erez <merez@codeaurora.org>
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: wil6210@qti.qualcomm.com
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/20200827073718.GV3248864@dell