Add callback into vendor interface to receive modem state change event am: 7b4a7557

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/opt/telephony/+/26594161



Change-Id: Ie0d5ed39fe93e7a0d453ea536b764cc27adbc7ca
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>