wifi: rtw89: call rtw89_chan_get() by vif chanctx if aware of vif

We adjust these processes which can work accodrding to vif but call
rtw89_chan_get() with static RTW89_SUB_ENTITY_0. After multi-channel
support, chanctx of vif won't always be on RTW89_SUB_ENTITY_0. So,
we make them call rtw89_chan_get() with rtwvif->sub_entity_idx.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230816082133.57474-5-pkshih@realtek.com