Modernize codebase by replacing NULL with nullptr

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

Test: m
Bug: 68236239
Change-Id: I23c4346097d1e7cfbbd7225913a4d187a05f7506

IInterface.cpp

diff --git a/IInterface.cpp b/IInterface.cpp
index 01866e6..3545325 100644
--- a/IInterface.cpp
+++ b/IInterface.cpp
@@ -33,14 +33,14 @@
 // static
 sp<IBinder> IInterface::asBinder(const IInterface* iface)
 {
-    if (iface == NULL) return NULL;
+    if (iface == nullptr) return nullptr;
     return const_cast<IInterface*>(iface)->onAsBinder();
 }
 
 // static
 sp<IBinder> IInterface::asBinder(const sp<IInterface>& iface)
 {
-    if (iface == NULL) return NULL;
+    if (iface == nullptr) return nullptr;
     return iface->onAsBinder();
 }