QPlatformWindow: fix isAncestorOf not breaking recursion
The current implementation got stuck always asking for the parent of the same child
This patch will make sure we actually walk up the parent chain.
Pick-to: 6.2 6.2.0 6.1 5.15
Change-Id: I9f67f6305e0143526f53952a563d496e760ac2e7
Reviewed-by: Tor Arne Vestbø tor.arne.vestbo@qt.io
(cherry picked from commit f06f3977)