wifi: rtw89: Fix TX fail with A2DP after scanning

There might be some racing between BT and WiFi after scan. Since
one of the TX related register will be modified by both FW and
rtw89_set_channel() in driver, which could cause Tx fail. Reorder
the calling sequence to only notify coexistence mechanism after
rtw89_set_channel() is called, so that there are no concurrent
operations.

Fixes: 5f499ce6 ("wifi: rtw89: pause/proceed MCC for ROC and HW scan")
Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20241021063219.22613-1-pkshih@realtek.com