wifi: rtw88: 8812a: Mitigate beacon loss

wifi: rtw88: 8812a: Mitigate beacon loss

The RTL8812AU has a reception problem, maybe only in the 5 GHz band.
Sometimes, in some positions, it stops receiving anything even though
the distance to the AP is only ~3 meters and there are no obstacles.
Moving it a few centimeters fixes it.

Switch the initial gain to maximum coverage when there is beacon loss.
This only helps sometimes. This is similar to what the official driver
does.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/203f5043-4fe1-4f35-8b8f-d3b6f44e1fd9@gmail.com