[inputflinger] Modernize codebase by replacing NULL with nullptr

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

Test: m
Bug: 68236239
Change-Id: I0d06ab2a187e72bd893900355edad97caa684c7a
diff --git a/services/inputflinger/EventHub.h b/services/inputflinger/EventHub.h
index 66bc294..dfe3def 100644
--- a/services/inputflinger/EventHub.h
+++ b/services/inputflinger/EventHub.h
@@ -385,7 +385,7 @@
         const bool isVirtual; // set if fd < 0 is passed to constructor
 
         const sp<KeyCharacterMap>& getKeyCharacterMap() const {
-            if (combinedKeyMap != NULL) {
+            if (combinedKeyMap != nullptr) {
                 return combinedKeyMap;
             }
             return keyMap.keyCharacterMap;