In some cases userspace may need to create dmabuffers from userspace
on such example is the software ISP part of libcamera which needs to
allocate dma-buffers for the output of the software ISP.
At first the plan was to allow console users access to /dev/dma_heap/*,
this was discussed with various kernel folks here:
https://lore.kernel.org/all/bb372250-e8b8-4458-bc99-dd8365b06991@redhat.com/
Giving console users access to the dma_heap's was deemed a bad idea
because memory allocated this way is not accounted in cgroup limits.
Giving access to /dev/udmabuf OTOH was deemed acceptable so that
is what this patch adds.
Resolves: #32662
