wifi: rsi: rsi_91x_hal: Remove unnecessary conversions

No need cast (struct rsi_hw *) to (struct rsi_hw *).

Signed-off-by: Wu Yunchuan <yunchuan@nfschina.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230803073507.3666471-1-yunchuan@nfschina.com