According to the comment removing non host visible heaps
was only meant for non-ReBAR. We can detect ReBAR and
allow host image copy on non host visible heaps.
Also drops an old comment from the first rudimentary
implementation of this function.
Results for *host_image_copy* on a Ada gpu with ReBAR.
Test run totals:
Passed: 51686/149362 (34.6%)
Failed: 0/149362 (0.0%)
Not supported: 97676/149362 (65.4%)
Warnings: 0/149362 (0.0%)
Waived: 0/149362 (0.0%)
Reviewed-by: Mohamed Ahmed <mohamedahmedegypt2001@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37385>
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