[BUGFIX] Excessive number of copy kernel calls

[oleksandr-pavlyk]

Using ze_tracer from pti-gpu/ repo reported two kernel calls for every setitem call.

Missing return was the culprit

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/795/index.html

[coveralls]

Coverage decreased (-0.01%) to 81.87% when pulling 60e06dd on avoid-extra-copy-call into 8e06a6c on master.

[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞