wifi: rsi: rsi_91x_mac80211: Remove unnecessary conversions

No need cast (struct rsi_hw *) to (struct rsi_hw *),
or cast (struct rsi_common *) to (struct rsi_common *).

Signed-off-by: Wu Yunchuan <yunchuan@nfschina.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230803073517.3666559-1-yunchuan@nfschina.com