wifi: rtw88: Increase the RX gain before scanning

wifi: rtw88: Increase the RX gain before scanning

The driver reduces the RX gain while connected to a network located
close by. In this condition scans return few results because the more
distant networks can't be heard.

Temporarily increase the RX gain before scanning in order to detect
all available networks. Reset the RX gain back to the last recorded
value once the scan finishes.

Link: https://github.com/lwfinger/rtw88/issues/337
Signed-off-by: Martin Hrůza <martin.hruza123@gmail.com>
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/c2e72aff-190d-4f59-9914-2588de756385@gmail.com