When allocating 2MB chunks of memory, the kernel can use 64K pages if
both the virtual and physical addresses are aligned to 2MB. While we
can't control the physical allocation, we can ensure the virtual address
we use with softpin meets the requirements.
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25447>