Bluetooth: drivers/nble: Fix returning included service handle

Parse include function intention is to return last parsed included
service handle. Next discovery iteration of included services should be
started from last found included service handle instead of end handle
from included handle value (which contains attribute handle of included
service declaration and the end group handle, BLUETOOTH SPECIFICATION
Version 4.2 [Vol 3, Part G], 4.5.1).

Change-Id: I73fe4027cb616242e838ea54c61b7780f1838e52
Signed-off-by: Grzegorz Kolodziejczyk <grzegorz.kolodziejczyk@tieto.com>