FW stats does provide the Rx rate information. Add this.
Tested with firmware 10x firmware.

Increase buffer size so more peers can be shown.
Signed-off-by: NChun-Yeow Yeoh <yeohchunyeow@gmail.com>
Signed-off-by: NBen Greear <greearb@candelatech.com>
Signed-off-by: NKalle Valo <kvalo@qca.qualcomm.com>