RDMA/core: Save the MR type in the ib_mr structure

This is a preparation for the signature verbs API change. This change is
needed since the MR type will define, in the upcoming patches, the need
for allocating internal resources in LLD for signature handover related
operations. It will also help to make sure that signature related
functions are called with an appropriate MR type and fail otherwise.
Also introduce new mr types IB_MR_TYPE_USER, IB_MR_TYPE_DMA and
IB_MR_TYPE_DM for correctness.

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>