syscalls/sync03: Remove useless judgement

The TEST_VOID was defined as below in include/tst_test.h
define TEST_VOID(SCALL) \
        do { \
                errno = 0; \
                SCALL; \
                TST_ERR = errno; \
        } while (0)

It doesn't assign the value fot TST_RET like TEST macro. So
remove the useless judgement and use sync instead because
sync() is always successful.

Signed-off-by: Yang Xu <[email protected]>
Reviewed-by: Cyril Hrubis <[email protected]>

Author: xuyang0410

testcases/kernel/syscalls/sync/sync03.c

@@ -37,10 +37,7 @@ static void verify_sync(void)
 
 	tst_fill_fd(fd, 0, TST_MB, FILE_SIZE_MB);
 
-	TEST_VOID(sync());
-
-	if (TST_RET)
-		tst_brk(TFAIL | TTERRNO, "sync() failed");
+	sync();
 
 	written = tst_dev_bytes_written(tst_device->dev);