FORTIFY_SOURCE could detect various overflows at compile and run time.
ARCH_HAS_FORTIFY_SOURCE means that the architecture can be built and run
with CONFIG_FORTIFY_SOURCE. So select it in LoongArch.
See more about this feature from commit 
6974f0c4555e285 ("include/linux/
string.h: add the option of fortified string.h functions").
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
        select ARCH_ENABLE_MEMORY_HOTPLUG
        select ARCH_ENABLE_MEMORY_HOTREMOVE
        select ARCH_HAS_ACPI_TABLE_UPGRADE      if ACPI
+       select ARCH_HAS_FORTIFY_SOURCE
        select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
        select ARCH_HAS_PTE_SPECIAL
        select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST