eatt: Fix for the crash on incoming channel creation

It fixes:

signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
Abort message: '[FATAL:eatt_impl.h(142)] Check failed: eatt_dev->eatt_tcb_.

Crash could happen when Android is connects at first as a central device
connection to peer which supports EATT and after reconnection it is peer
initiating ecoc (e.g. Android is peripheral or peer is faster with ecoc
connection request). At that point eatt_dev is there but eatt_tcb_ is
not.

Bug: 159786353
Bug: 191313013
Tag: #feature
Test: atest --host net_test_eatt
Sponsor: jpawlowski@

Merged-In: Ic5e8c027dc45eec942457f09c987ec64cfafb761
Change-Id: Ic5e8c027dc45eec942457f09c987ec64cfafb761