clang-tidy: Enable modernize-use-nullptr check

This check converts the usage of null pointer constants
(e.g. NULL, 0) to use the new C++11 and C23 nullptr keyword.

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I10dccfd0513385c583ca07d13ed71edb04b58853
diff --git a/.clang-tidy b/.clang-tidy
index d1d47cd..116e43b 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -222,6 +222,7 @@
 modernize-use-equals-default,
 modernize-use-equals-delete,
 modernize-use-noexcept,
+modernize-use-nullptr,
 modernize-use-override,
 modernize-use-transparent-functors,
 modernize-use-uncaught-exceptions,