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/include/asm/cache.h b/arch/blackfin/include/asm/cache.h
index 482e4b5..568885a 100644
--- a/arch/blackfin/include/asm/cache.h
+++ b/arch/blackfin/include/asm/cache.h
@@ -7,7 +7,7 @@
 #ifndef __ARCH_BLACKFIN_CACHE_H
 #define __ARCH_BLACKFIN_CACHE_H
 
-#include <asm/linkage.h>	/* for asmlinkage */
+#include <linux/linkage.h>	/* for asmlinkage */
 
 /*
  * Bytes per L1 cache line