We already have memory in the union here that is being wasted in AMD's
case, use it to store the nid.

Putting the nid here further isolates the io_pgtable code from the struct
protection_domain.

Fixup protection_domain_alloc so that the NID from the device is provided,
at this point dev is never NULL for AMD so this will now allocate the
first table pointer on the correct NUMA node.
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/8-v2-831cdc4d00f3+1a315-amd_iopgtbl_jgg@nvidia.comSigned-off-by: Joerg Roedel <jroedel@suse.de>