[SYCL][NFC] Fix a Coverity hit in device_image_impl ctor

[sergey-semenov]

No description provided.

[aelovikov-intel]

Not an expert on the best practices, but I think std::move could be better on average:

device_image_impl obj(..., create_rval_context(), ...); // 1
device_image_impl obj(..., lval_context, ...);          // 2

For by-value param followed by a std::move we'd have two move-ctors (1) and copy-ctor + move-ctor (2).

For by-const-ref we'll have copy-ctor (1) and copy-ctor. Effectively, we remove one move-ctor (cheap) in either case and introduce a more expensive copy-ctor in (1).

That said, it's probably unlikely to matter in practice, so LGTM.

+ @vinser52 in case we need to update our "informal style guides".

[sergey-semenov]

I changed it this way mostly to align with the rest of the constructors, but I do prefer pass-by-value then move as well. And, on closer inspection, we actually have a weird mix of the two in this file, so I'll update the PR to use that instead.