linkage.h: move from blackfin to common includes

1. Add linkage.h support from blackfin to common include,
   which is a reduced version from Linux.
2. Add architecture part support of linkage.h into blackfin
3. Fix include path of in blackfin related to linkage.h
   due to header file movement.

Signed-off-by: Macpaul Lin <macpaul@andestech.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/cpu/cache.S b/arch/blackfin/cpu/cache.S
index 6ed655a..5ca9e91 100644
--- a/arch/blackfin/cpu/cache.S
+++ b/arch/blackfin/cpu/cache.S
@@ -8,8 +8,8 @@
  * Licensed under the GPL-2 or later.
  */
 
-#include <asm/linkage.h>
 #include <config.h>
+#include <linux/linkage.h>
 #include <asm/blackfin.h>
 
 .text