lib/test_printf: Add test of null/invalid pointer dereference for dentry

This add some additional test cases of null/invalid pointer dereference
for dentry and file (%pd and %pD)

Link: http://lkml.kernel.org/r/20190809012457.56685-2-justin.he@arm.com


To: Geert Uytterhoeven <geert+renesas@glider.be>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Petr Mladek <pmladek@suse.com>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: "Tobin C. Harding" <tobin@kernel.org>
Signed-off-by: Jia He <justin.he@arm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>