arm64: defconfig: Enable Broadcom's GENET Ethernet controller

Currently used on the Raspberry Pi 4 and various Broadcom STB SoCs.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm64/configs/defconfig

@@ -253,6 +253,7 @@ CONFIG_VIRTIO_NET=y
 CONFIG_AMD_XGBE=y
 CONFIG_NET_XGENE=y
 CONFIG_ATL1C=m
+CONFIG_BCMGENET=m
 CONFIG_BNX2X=m
 CONFIG_MACB=y
 CONFIG_THUNDER_NIC_PF=y