arm64: uti: Add arch-dependent helper for context switch

arm64 performs context-switch in kernel space instead of user space as in
x86_64.

Change-Id: Ib119b9ff014effb970183ee86cfac67fab773cba
Futjitsu: POSTK_DEBUG_ARCH_DEP_99

executer/kernel/mcctrl/arch/x86_64/archdeps.c

@@ -368,3 +368,11 @@ static inline bool pte_is_write_combined(pte_t pte)
 }
 #endif /* POSTK_DEBUG_ARCH_DEP_12 */
 
+/*
+ * The assembler switch_ctx is save/load registers in the context.
+ * Do FS save/load and register host_thread with ioctl.
+ */
+long arch_switch_ctx(struct uti_save_fs_desc *desc)
+{
+	return 0;
+}