clv: Change no_preempt from int to ihk_atomic_t.

Fix the issue where the value of no_preempt gets unexpected value
(-1, 1, 2 etc.) after process ends when running the UTI tests.

Change-Id: I7d9c08b754a171ea3fdec20ab2e635df3b607cbd

kernel/syscall.c

@@ -260,7 +260,8 @@ long do_syscall(struct syscall_request *req, int cpu)
 			cpu_pause();
 
 			/* Spin if not preemptable */
-			if (cpu_local_var(no_preempt) || !thread->tid) {
+			if (ihk_atomic_read(&cpu_local_var(no_preempt))
+				|| !thread->tid) {
 				continue;
 			}