POST: move CONFIG_POST to Makefiles

Introduce the new logical option CONFIG_HAS_POST which is set when the
platform has CONFIG_POST set. Use CONFIG_HAS_POST in the post/ Makefiles
to determine should the POST libs be compiled for the selected target
platform, or not.

To avoid breaking u-boot linking process, the empty post/libpost.a file is
created for platforms which do not have POSTs.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/include/common.h b/include/common.h
index 673afdd..8d435b9 100644
--- a/include/common.h
+++ b/include/common.h
@@ -672,4 +672,15 @@
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
+/* Multicore arch functions */
+#ifdef CONFIG_MP
+int cpu_status(int nr);
+int cpu_reset(int nr);
+int cpu_release(int nr, int argc, char *argv[]);
+#endif
+
+#ifdef CONFIG_POST
+#define CONFIG_HAS_POST
+#endif
+
 #endif	/* __COMMON_H_ */