Add feature flag for Emergency Callback Mode Notification

This commit adds feature flag for Emergency Callback Mode Notification.
This flag allows the use to notify the emergency callback mode for
call/SMS to other applications.

Bug: 359064059
Test: build pass
Flag: com.android.internal.telephony.flags.emergency_callback_mode_notification

Change-Id: I36c28091a88973dea83d2f9d1d4943c06e2a8ca1
diff --git a/flags/calling.aconfig b/flags/calling.aconfig
index a5757d8..906abfc 100644
--- a/flags/calling.aconfig
+++ b/flags/calling.aconfig
@@ -62,3 +62,11 @@
         purpose: PURPOSE_BUGFIX
     }
 }
+
+# OWNER=yongnamcha TARGET=25Q2
+flag {
+    name: "emergency_callback_mode_notification"
+    namespace: "telephony"
+    description: "Used to notify the emergency callback mode for call/SMS to other applications."
+    bug:"359064059"
+}