Added PPPOE kernel config to fix PPPOE throughput issue

Change-Id: I48a9e983f30518db55bd73f2dcf774fd0f55ee09
Reviewed-on: https://tp-biosrd-v02/gerrit/87450
Reviewed-by: Jamess Huang(黃以民) <Jamess_Huang@asus.com>
Tested-by: Jamess Huang(黃以民) <Jamess_Huang@asus.com>

Author: alex3788

arch/arm/configs/miniarm-rk3288_defconfig

@@ -427,6 +427,7 @@ CONFIG_STMMAC_ETH=y
 CONFIG_ROCKCHIP_PHY=y
 CONFIG_PPP=y
 CONFIG_PPP_ASYNC=y
+CONFIG_PPPOE=y
 CONFIG_USB_PEGASUS=y
 CONFIG_USB_RTL8150=y
 CONFIG_USB_RTL8152=y