wifi: rtw88: Fix the random "error beacon valid" messages for USB

All the USB devices have a problem in AP mode: uploading the updated
beacon to the chip's reserved page can randomly fail:

[34996.474304] rtw88_8723du 1-2:1.2: error beacon valid
[34996.474788] rtw88_8723du 1-2:1.2: failed to download drv rsvd page
[34999.956369] rtw88_8723du 1-2:1.2: error beacon valid
[34999.956846] rtw88_8723du 1-2:1.2: failed to download drv rsvd page
[34999.956855] rtw88_8723du 1-2:1.2: failed to download beacon
[35017.978296] rtw88_8723du 1-2:1.2: error beacon valid
[35017.978805] rtw88_8723du 1-2:1.2: failed to download drv rsvd page
[35017.978823] rtw88_8723du 1-2:1.2: failed to download beacon
[35023.200395] rtw88_8723du 1-2:1.2: error beacon valid
[35023.200869] rtw88_8723du 1-2:1.2: failed to download drv rsvd page
[35023.200875] rtw88_8723du 1-2:1.2: failed to download beacon
[35478.680547] rtw88_8723du 1-2:1.2: error beacon valid
[35478.681023] rtw88_8723du 1-2:1.2: failed to download drv rsvd page

Disable some beacon-related hardware functions before uploading the
beacon and enable them again after.

Tested with RTL8723DU, RTL8812BU, RTL8822CE.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/c248c40a-d432-47ed-90e0-d81ee6c32464@gmail.com