Introduce a verbs interface for signature-related operations.  A
signature handover operation configures the layouts of data and
protection attributes both in memory and wire domains.

Signature operations are:

- INSERT:
  Generate and insert protection information when handing over
  data from input space to output space.
- validate and STRIP:
  Validate protection information and remove it when handing over
  data from input space to output space.
- validate and PASS:
  Validate protection information and pass it when handing over
  data from input space to output space.

Once the signature handover opration is done, the HCA will offload
data integrity generation/validation while performing the actual data
transfer.

Additions:

1. HCA signature capabilities in device attributes
    Verbs provider supporting signature handover operations fills
    relevant fields in device attributes structure returned by
    ib_query_device.

2. QP creation flag IB_QP_CREATE_SIGNATURE_EN
    Creating a QP that will carry signature handover operations may
    require some special preparations from the verbs provider.  So we
    add QP creation flag IB_QP_CREATE_SIGNATURE_EN to declare that the
    created QP may carry out signature handover operations.  Expose
    signature support to verbs layer (no support for now).

3. New send work request IB_WR_REG_SIG_MR
    Signature handover work request. This WR will define the signature
    handover properties of the memory/wire domains as well as the
    domains layout. The purpose of this work request is to bind all
    the needed information for the signature operation:

    - data to be transferred:  wr->sg_list (ib_sge).
      * The raw data, pre-registered to a single MR (normally, before
        signature, this MR would have been used directly for the data
        transfer)
    - data protection guards: sig_handover.prot (ib_sge).
      * The data protection buffer, pre-registered to a single MR, which
        contains the data integrity guards of the raw data blocks.
        Note that it may not always exist, only in cases where the user is
        interested in storing protection guards in memory.
    - signature operation attributes: sig_handover.sig_attrs.
      * Tells the HCA how to validate/generate the protection information.

    Once the work request is executed, the memory region that will
    describe the signature transaction will be the sig_mr.  The
    application can now go ahead and send the sig_mr.rkey or use the
    sig_mr.lkey for data transfer.

4. New Verb ib_check_mr_status
    check_mr_status verb checks the status of the memory region post
    transaction.  The first check that may be used is
    IB_MR_CHECK_SIG_STATUS, which will indicate if any signature
    errors are pending for a specific signature-enabled ib_mr.  This
    verb is a lightwight check and is allowed to be taken from
    interrupt context.  An application must call this verb after it is
    known that the actual data transfer has finished.
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>