leaudio: Fix characteristic subscribtion on reconnection

When remote device is bonded it should keep CCC state, however Android
assures that every connection.

With this patch, CCC registration will happen after encryption is
enabled to avoid Write rejection.

Bug: 235190324
Test: atest BluetoothInstrumentationTests
Tag: #feature
Change-Id: Idda5dc54a9332ae35b8995d26a4441a50a13f67c