gatt: Fix invalid EATT disconnection

In following scenario, EATT channels will be incorrectly disconnected

1. Connect Dual Mode device on both transports.
2. Connect EATT over LE
3. Try to connect ATT over BR/EDR
4. Remote fails to connect ATT over BR/EDR
5. Error happens -> EATT is disconnected

Note, Android supports EATT only on LE.

Bug: 355767463
Flag: Exempt, obvious fix
Test: mmm packages/modules/Bluetooth
Change-Id: Icd0bfe4dfdc0c0b9aa2345fa2370a46df68fc951