arm64: defconfig: Enable PCI generic host bridge by default

Now that pci-host-generic can be used under arm64, enable it by
default so that SBSA compliant systems can use it.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>

arch/arm64/configs/defconfig

@@ -49,6 +49,7 @@ CONFIG_ARCH_XGENE=y
 CONFIG_ARCH_ZYNQMP=y
 CONFIG_PCI=y
 CONFIG_PCI_MSI=y
+CONFIG_PCI_HOST_GENERIC=y
 CONFIG_PCI_XGENE=y
 CONFIG_SMP=y
 CONFIG_PREEMPT=y