MIPS: Loongson64: Fix build error 'secondary_kexec_args' undeclared under !SMP

On the Loongson64 platform, if CONFIG_SMP is not set, the following build
error will occur:
arch/mips/loongson64/reset.c:133:2: error:'secondary_kexec_args' undeclared

Because the definition and declaration of secondary_kexec_args are in the
CONFIG_SMP, the secondary_kexec_args variable should be used in CONFIG_SMP.

Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Youling Tang <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/loongson64/reset.c

···
 	for_each_possible_cpu(cpu)
 		if (!cpu_online(cpu))
 			cpu_device_up(get_cpu_device(cpu));
+
+	secondary_kexec_args[0] = TO_UNCAC(0x3ff01000);
 #endif
 	kexec_args[0] = kexec_argc;
 	kexec_args[1] = fw_arg1;
 	kexec_args[2] = fw_arg2;
-	secondary_kexec_args[0] = TO_UNCAC(0x3ff01000);
 	memcpy((void *)fw_arg1, kexec_argv, KEXEC_ARGV_SIZE);
 	memcpy((void *)fw_arg2, kexec_envp, KEXEC_ENVP_SIZE);
 }
···
 	kexec_args[0] = kdump_argc;
 	kexec_args[1] = fw_arg1;
 	kexec_args[2] = fw_arg2;
+#ifdef CONFIG_SMP
 	secondary_kexec_args[0] = TO_UNCAC(0x3ff01000);
+#endif
 	memcpy((void *)fw_arg1, kdump_argv, KEXEC_ARGV_SIZE);
 	memcpy((void *)fw_arg2, kexec_envp, KEXEC_ENVP_SIZE);
 }