arm64: core support

Relocation code based on a patch by Scott Wood, which is:
Signed-off-by: Scott Wood <scottwood@freescale.com>

Signed-off-by: David Feng <fenghua@phytium.com.cn>
diff --git a/include/image.h b/include/image.h
index ee6eb8d..7de2bb2 100644
--- a/include/image.h
+++ b/include/image.h
@@ -156,6 +156,7 @@
 #define IH_ARCH_SANDBOX		19	/* Sandbox architecture (test only) */
 #define IH_ARCH_NDS32	        20	/* ANDES Technology - NDS32  */
 #define IH_ARCH_OPENRISC        21	/* OpenRISC 1000  */
+#define IH_ARCH_ARM64		22	/* ARM64	*/
 
 /*
  * Image Types