leaudio: Fix setting disconnecting state for ASEs

Without this patch, when stream is canceled in Enabling state, when
CISes are not yet created and Data Path is not set, btm_iso
DisconnectCis could be called twice for bidirectional CIS and this could
lead to assert in btm_iso.

Bug: 376396494
Flag: Exempt, trivial and obvious fix.
Test: atest bluetooth_le_audio_test
Change-Id: I9df7b6e1c7bd706676a22c76e81c4b1e1cb29d2b