[adb] Modernize codebase by replacing NULL with nullptr

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

Test: m
Bug: 68236239
Change-Id: Ia8c4deacafed2f3b7dbc3d4c3c77c6c632e3de81
diff --git a/adb/daemon/usb.cpp b/adb/daemon/usb.cpp
index c724b11..51ad5f5 100644
--- a/adb/daemon/usb.cpp
+++ b/adb/daemon/usb.cpp
@@ -359,7 +359,7 @@
         }
 
         LOG(INFO) << "registering usb transport";
-        register_usb_transport(usb, 0, 0, 1);
+        register_usb_transport(usb, nullptr, nullptr, 1);
     }
 
     // never gets here