Modernize codebase by replacing NULL with nullptr

Fixes -Wzero-as-null-pointer-constant warning.

Test: m
Bug: 68236239
Change-Id: I23c4346097d1e7cfbbd7225913a4d187a05f7506
diff --git a/Debug.cpp b/Debug.cpp
index d304d21..38e3a3f 100644
--- a/Debug.cpp
+++ b/Debug.cpp
@@ -166,13 +166,13 @@
         else if (bytesPerLine >= 8) alignment = 2;
         else alignment = 1;
     }
-    if (func == NULL) func = defaultPrintFunc;
+    if (func == nullptr) func = defaultPrintFunc;
 
     size_t offset;
 
     unsigned char *pos = (unsigned char *)buf;
 
-    if (pos == NULL) {
+    if (pos == nullptr) {
         if (singleLineBytesCutoff < 0) func(cookie, "\n");
         func(cookie, "(NULL)");
         return;
@@ -302,7 +302,7 @@
 
 ssize_t getHWBinderKernelReferences(size_t count, uintptr_t* buf) {
     sp<ProcessState> proc = ProcessState::selfOrNull();
-    if (proc.get() == NULL) {
+    if (proc.get() == nullptr) {
         return 0;
     }