wifi: mwifiex: cleanup private data structures

Drop unused fields 'status_code' of 'struct mwifiex_txinfo',
'dfs_chan_switch_timer', 'sleep_params' (including related data
type 'struct mwifiex_sleep_params') of 'struct mwifiex_adapter',
adjust related code.

Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230802160726.85545-2-dmantipov@yandex.ru