add arm64 support

- add arm64 dependent codes with GICv3 and SVE support
- fix bugs based on architecture separation requests

arch/arm64/kernel/include/context.h

@@ -0,0 +1,8 @@
+/* context.h COPYRIGHT FUJITSU LIMITED 2015 */
+#ifndef __HEADER_ARM64_COMMON_CONTEXT_H
+#define __HEADER_ARM64_COMMON_CONTEXT_H
+
+void switch_mm(struct page_table *pgtbl);
+void free_mmu_context(struct page_table *pgtbl);
+
+#endif /*__HEADER_ARM64_COMMON_CONTEXT_H*/