[Kernel] Change the version number to 2.0.0.

include/rtdef.h

@@ -48,8 +48,8 @@ extern "C" {
 /*@{*/
 
 /* RT-Thread version information */
-#define RT_VERSION                      1L              /**< major version number */
-#define RT_SUBVERSION                   2L              /**< minor version number */
+#define RT_VERSION                      2L              /**< major version number */
+#define RT_SUBVERSION                   0L              /**< minor version number */
 #define RT_REVISION                     0L              /**< revise version number */
 
 /* RT-Thread version */