Blackfin: SMP: fix build breakage in cache.h

The SMP code needs "asmlinkage" which linkage.h provides.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/cache.h

@@ -7,6 +7,8 @@
 #ifndef __ARCH_BLACKFIN_CACHE_H
 #define __ARCH_BLACKFIN_CACHE_H
 
+#include <linux/linkage.h>	/* for asmlinkage */
+
 /*
  * Bytes per L1 cache line
  * Blackfin loads 32 bytes for cache