Fix: give an event for AVDT_DELAY_REPORT_CFM_EVT

AVDT_DELAY_REPORT_CFM_EVT is mistakenly mapped to 0 (BTA_AV)
event. This caused crash when delay report is supported and
delay report responses have been received.

Now creating a delay report confirm event so it can be handled
later in bta av system

Bug: 188367563
Tag: #feature
Test: atest --host bluetooth_test_gd
Change-Id: Icbe01569d90abd4a881489e013a111432cf53d01