clang-tidy: Replace NULL with nullptr

Replaced all instances of NULL with nullptr to improve type safety
and clarity, as nullptr is the modern C++ standard for null pointers.

Tested: Build verified

Change-Id: I1771e207ce2171990fcf55a6f29292f4c70f1284
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/snmp_util.cpp b/snmp_util.cpp
index bc46c99..b8ed839 100644
--- a/snmp_util.cpp
+++ b/snmp_util.cpp
@@ -52,7 +52,7 @@
     hints.ai_socktype = SOCK_STREAM;
     hints.ai_flags |= AI_CANONNAME;
 
-    auto result = getaddrinfo(address.c_str(), NULL, &hints, &addr);
+    auto result = getaddrinfo(address.c_str(), nullptr, &hints, &addr);
     if (result)
     {
         lg2::error("getaddrinfo failed {ADDRESS}: {RC}", "ADDRESS", address,
@@ -65,7 +65,7 @@
 
     char ipaddress[INET6_ADDRSTRLEN]{0};
     result = getnameinfo(addrPtr->ai_addr, addrPtr->ai_addrlen, ipaddress,
-                         sizeof(ipaddress), NULL, 0, NI_NUMERICHOST);
+                         sizeof(ipaddress), nullptr, 0, NI_NUMERICHOST);
     if (result)
     {
         lg2::error("getnameinfo failed {ADDRESS}: {RC}", "ADDRESS", address,