libcamera: DmaBufAllocator: Support allocating from /dev/udmabuf

The dma-buf allocator currently allocates from CMA and system heaps.

Extend the dma-buf allocator to support allocating dma-buffers by creating
memfd-s and turning those into dma-buffers using /dev/udmabuf.

The buffers allocated through memfd/udmabuf are not suitable for zero-copy
buffer sharing with other devices.

Co-developed-by: Harvey Yang <chenghaoyang@chromium.org>
Signed-off-by: Harvey Yang <chenghaoyang@chromium.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # Lenovo-x13s
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>