[input] Modernize codebase by replacing NULL with nullptr

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

Test: m
Bug: 68236239
Change-Id: I8882234efd2a0b3ef27472d3f5d4e9c69c6e7b37
diff --git a/libs/input/VelocityTracker.cpp b/libs/input/VelocityTracker.cpp
index 496158b..118f3aa 100644
--- a/libs/input/VelocityTracker.cpp
+++ b/libs/input/VelocityTracker.cpp
@@ -115,7 +115,7 @@
 
     // Allow the default strategy to be overridden using a system property for debugging.
     if (!strategy) {
-        int length = property_get("persist.input.velocitytracker.strategy", value, NULL);
+        int length = property_get("persist.input.velocitytracker.strategy", value, nullptr);
         if (length > 0) {
             strategy = value;
         } else {
@@ -139,7 +139,7 @@
 
 bool VelocityTracker::configureStrategy(const char* strategy) {
     mStrategy = createStrategy(strategy);
-    return mStrategy != NULL;
+    return mStrategy != nullptr;
 }
 
 VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
@@ -204,7 +204,7 @@
         // time to adjust to changes in direction.
         return new LegacyVelocityTrackerStrategy();
     }
-    return NULL;
+    return nullptr;
 }
 
 void VelocityTracker::clear() {