common: do not fit to unknown device memory (#22614)

* common: do not fit to unknown device memory

Signed-off-by: Florian Reinle <f.reinle@otec.de>

* common: preserve host fallback for non-GPU fit devices

Signed-off-by: Florian Reinle <f.reinle@otec.de>

* common: keep unknown GPU fit memory at zero

Signed-off-by: Florian Reinle <f.reinle@otec.de>

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Signed-off-by: Florian Reinle <f.reinle@otec.de>