Also add documentation for 'mvm'.

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

 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:400: warning: cannot understand function prototype: 'const u16 expected_tpt_legacy[IWL_RATE_COUNT] = '
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'mvm' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'tbl' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'scale_index' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'attempts' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'successes' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:684: warning: Function parameter or member 'window' not described in '_rs_collect_tx_data'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2677: warning: duplicate section name 'NOTE'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2682: warning: Function parameter or member 'mvm' not described in 'rs_initialize_lq'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2682: warning: Function parameter or member 'sta' not described in 'rs_initialize_lq'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2682: warning: Function parameter or member 'lq_sta' not described in 'rs_initialize_lq'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2682: warning: Function parameter or member 'band' not described in 'rs_initialize_lq'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:3761: warning: Function parameter or member 'mvm' not described in 'rs_program_fix_rate'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:3761: warning: Function parameter or member 'lq_sta' not described in 'rs_program_fix_rate'
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c:4213: warning: Function parameter or member 'mvm' not described in 'iwl_mvm_tx_protection'

Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Cc: Luca Coelho <luciano.coelho@intel.com>
Cc: Intel Linux Wireless <linuxwifi@intel.com>
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: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201126133152.3211309-3-lee.jones@linaro.org