Add smp support to RT-Thread 4.0

src/Kconfig

@@ -8,6 +8,22 @@ config RT_NAME_MAX
         Each kernel object, such as thread, timer, semaphore etc, has a name,
         the RT_NAME_MAX is the maximal size of this object name.
 
+config RT_USING_SMP
+    bool "Enable SMP(Symmetric multiprocessing)"
+    default n
+	help
+        This option should be selected by machines which have an SMP-
+        capable CPU.
+        The only effect of this option is to make the SMP-related
+        options available to the user for configuration.
+
+config RT_CPUS_NR
+    int "Number of CPUs"
+	default 2
+	depends on RT_USING_SMP
+    help
+		Number of CPUs in the system
+
 config RT_ALIGN_SIZE
     int "Alignment size for CPU architecture data access"
     default 4