Streamline stack/l2cap/l2c_ble::l2cble_notify_le_connection

Towards readable code

Bug: 163134718
Tag: #refactor
Test: act.py -tc BleCocTest
Test: ble paired 2 phones
Test: classic paired Bose SoundLink
Change-Id: I1ffb5df7acd8f616822ec3eeacef7d88d6dbc249