rusticl/kernel: Fix creation from programs not built for every device

rusticl/kernel: Fix creation from programs not built for every device

OpenCL does not require that a kernel is created for every device. So we
shouldn't assume there is a build for every device.

API validation around launching kernels already takes this possibility
into account.

I did not verify if the commit below is actually the culprit and whether
this bug existed before that, but a fix for older code also would have to
look differently anyway.

Fixes: 323dcbb4b52 ("rusticl: Move NirKernelBuild to ProgramDevBuild")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9968
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25696>