Mark BiometricUnlockController as @Singleton

We were creating more than one, which was causing NPEs.

Test: atest
Bug: 143258869
Change-Id: I500fdb62a53ab95a532777a667933c93a140b91b
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/BiometricUnlockController.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/BiometricUnlockController.java
index bd3d848..ffcbc40 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/BiometricUnlockController.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/BiometricUnlockController.java
@@ -47,10 +47,12 @@
 import java.lang.annotation.RetentionPolicy;
 
 import javax.inject.Inject;
+import javax.inject.Singleton;
 
 /**
  * Controller which coordinates all the biometric unlocking actions with the UI.
  */
+@Singleton
 public class BiometricUnlockController extends KeyguardUpdateMonitorCallback {
 
     private static final String TAG = "BiometricUnlockCtrl";