GATT: make last service end group handle equal to 0xFFFF

ESR06 (errata 4065) added sentence:
"The End Group Handle of the last service in a device can be 0xFFFF."
It talks about last service, not last primary service. Right now,
secondary service added after last primary service will result in in
last primary service being corrupted - descriptor added to last
characteristic, and some characteristics added.

Bug: 78107486
Change-Id: I6a146fce2c946cdff176ff79f147830e29d3b807