[libutils]  Modernize codebase by replacing NULL with nullptr

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

Test: m
Bug: 68236239
Change-Id: I5e89ec8c42151875439d2656475a8739ab9cb7dc
diff --git a/libutils/FileMap.cpp b/libutils/FileMap.cpp
index 3c4d81c..583c6b9 100644
--- a/libutils/FileMap.cpp
+++ b/libutils/FileMap.cpp
@@ -48,10 +48,10 @@
 
 // Constructor.  Create an empty object.
 FileMap::FileMap(void)
-    : mFileName(NULL),
-      mBasePtr(NULL),
+    : mFileName(nullptr),
+      mBasePtr(nullptr),
       mBaseLength(0),
-      mDataPtr(NULL),
+      mDataPtr(nullptr),
       mDataLength(0)
 #if defined(__MINGW32__)
       ,
@@ -69,9 +69,9 @@
       , mFileHandle(other.mFileHandle), mFileMapping(other.mFileMapping)
 #endif
 {
-    other.mFileName = NULL;
-    other.mBasePtr = NULL;
-    other.mDataPtr = NULL;
+    other.mFileName = nullptr;
+    other.mBasePtr = nullptr;
+    other.mDataPtr = nullptr;
 #if defined(__MINGW32__)
     other.mFileHandle = INVALID_HANDLE_VALUE;
     other.mFileMapping = NULL;
@@ -86,9 +86,9 @@
     mDataOffset = other.mDataOffset;
     mDataPtr = other.mDataPtr;
     mDataLength = other.mDataLength;
-    other.mFileName = NULL;
-    other.mBasePtr = NULL;
-    other.mDataPtr = NULL;
+    other.mFileName = nullptr;
+    other.mBasePtr = nullptr;
+    other.mDataPtr = nullptr;
 #if defined(__MINGW32__)
     mFileHandle = other.mFileHandle;
     mFileMapping = other.mFileMapping;
@@ -101,7 +101,7 @@
 // Destructor.
 FileMap::~FileMap(void)
 {
-    if (mFileName != NULL) {
+    if (mFileName != nullptr) {
         free(mFileName);
     }
 #if defined(__MINGW32__)
@@ -196,7 +196,7 @@
     if (!readOnly)
         prot |= PROT_WRITE;
 
-    ptr = mmap(NULL, adjLength, prot, flags, fd, adjOffset);
+    ptr = mmap(nullptr, adjLength, prot, flags, fd, adjOffset);
     if (ptr == MAP_FAILED) {
         ALOGE("mmap(%lld,%zu) failed: %s\n",
             (long long)adjOffset, adjLength, strerror(errno));
@@ -205,7 +205,7 @@
     mBasePtr = ptr;
 #endif // !defined(__MINGW32__)
 
-    mFileName = origFileName != NULL ? strdup(origFileName) : NULL;
+    mFileName = origFileName != nullptr ? strdup(origFileName) : nullptr;
     mBaseLength = adjLength;
     mDataOffset = offset;
     mDataPtr = (char*) mBasePtr + adjust;