RDMA/rxe: Allow registering persistent flag for pmem MR only

Memory region could  support at most 2 flush access flags:
IB_ACCESS_FLUSH_PERSISTENT and IB_ACCESS_FLUSH_GLOBAL

But we only allow user to register persistent flush flags to the pmem MR
where it has the ability of persisting data across power cycles.

So registering a persistent access flag to a non-pmem MR will be rejected.

Link: https://lore.kernel.org/r/20221206130201.30986-5-lizhijian@fujitsu.com


CC: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>