RDMA/core: Track device memory MRs

RDMA/core: Track device memory MRs

Device memory (DM) are registered as MR during initialization flow, these
MRs were not tracked by resource tracker and had res->valid set as a
false. Update the code to manage them too.

Before this change:
$ ibv_rc_pingpong -j &
$ rdma res show mr <-- shows nothing

After this change:
$ ibv_rc_pingpong -j &
$ rdma res show mr
dev ibp0s9 mrn 0 mrlen 4096 pdn 3 pid 734 comm ibv_rc_pingpong

Fixes: be934cca9e98 ("IB/uverbs: Add device memory registration ioctl support")
Link: https://lore.kernel.org/r/20201117070148.1974114-2-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>