Add support to get MR (mkey) resource dump in RAW format.

Link: https://lore.kernel.org/r/20200623113043.1228482-12-leon@kernel.orgSigned-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>