arm64: defconfig: Enable Broadcom's STB PCIe controller

For now mainly used in the Raspberry Pi 4.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm64/configs/defconfig

@@ -190,6 +190,7 @@ CONFIG_PCIE_ALTERA_MSI=y
 CONFIG_PCI_HOST_THUNDER_PEM=y
 CONFIG_PCI_HOST_THUNDER_ECAM=y
 CONFIG_PCIE_ROCKCHIP_HOST=m
+CONFIG_PCIE_BRCMSTB=m
 CONFIG_PCI_LAYERSCAPE=y
 CONFIG_PCI_HISI=y
 CONFIG_PCIE_QCOM=y