LoongArch: Set CPU#0 as the io master for FDT

ACPI systems set io masters by parsing ACPI MADT, FDT systems have no
MADT so we explicitly set CPU#0 as the io master. Otherwise CPU#0 will
be considered as hotpluggable.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/smp.c

@@ -210,6 +210,7 @@ static void __init fdt_smp_setup(void)
 	}
 
 	loongson_sysconf.nr_cpus = num_processors;
+	set_bit(0, &(loongson_sysconf.cores_io_master));
 #endif
 }