hw/rdma: Implementation of PVRDMA device

hw/rdma: Implementation of PVRDMA device

PVRDMA is the QEMU implementation of VMware's paravirtualized RDMA device.
It works with its Linux Kernel driver AS IS, no need for any special
guest modifications.

While it complies with the VMware device, it can also communicate with
bare metal RDMA-enabled machines and does not require an RDMA HCA in the
host, it can work with Soft-RoCE (rxe).

It does not require the whole guest RAM to be pinned allowing memory
over-commit and, even if not implemented yet, migration support will be
possible with some HW assistance.

Implementation is divided into 2 components, rdma general and pvRDMA
specific functions and structures.

The second PVRDMA sub-module - interaction with PCI layer.
- Device configuration and setup (MSIX, BARs etc).
- Setup of DSR (Device Shared Resources)
- Setup of device ring.
- Device management.

Reviewed-by: Dotan Barak <dotanb@mellanox.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>