wifi: rtl8xxxu: Report the RSSI to the firmware

Or in the case of RTL8188EU, report the RSSI to the rate control code.

The rate control code for RTL8188EU is less likely to switch to a lower
rate when the RSSI is high. The firmware-based rate control in the other
chips probably works the same way.

This affects all the chips, but it was only tested with RTL8188EU,
RTL8188FU, and RTL8192EU.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/2aab4f3f-e914-4fe1-f29a-deac91774d05@gmail.com