fix: y2038: hide timeval/timespec/itimerval/itimerspec types (v5.6)

See upstream commit:

  commit c766d1472c70d25ad475cf56042af1652e792b23
  Author: Arnd Bergmann <arnd@arndb.de>
  Date:   Thu Feb 20 20:03:57 2020 -0800

    y2038: hide timeval/timespec/itimerval/itimerspec types

    There are no in-kernel users remaining, but there may still be users that
    include linux/time.h instead of sys/time.h from user space, so leave the
    types available to user space while hiding them from kernel space.

    Only the __kernel_old_* versions of these types remain now.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I986a813ad8b1c753ab1fa07f726b0cc481f049cb

lttng-syscalls.c

@@ -77,6 +77,13 @@ struct user_msghdr;
  * Forward declaration for kernels >= 5.6
  */
 struct timex;
+struct timeval;
+struct itimerval;
+struct itimerspec;
+
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0))
+typedef __kernel_old_time_t time_t;
+#endif
 
 #ifdef IA32_NR_syscalls
 #define NR_compat_syscalls IA32_NR_syscalls