vmxnet3: introduce command to register memory region

In vmxnet3 version 3, the emulation added support for the vmxnet3 driver
to communicate information about the memory regions the driver will use
for rx/tx buffers. The driver can also indicate which rx/tx queue the
memory region is applicable for. If this information is communicated
to the emulation, the emulation will always keep these memory regions
mapped, thereby avoiding the mapping/unmapping overhead for every packet.

Currently, Linux vmxnet3 driver does not leverage this capability. The
feasibility of using this approach for the Linux vmxnet3 driver will be
investigated independently and if possible, will be part of a different
patch. This patch only exposes the emulation capability to the driver
(vmxnet3_defs.h is identical between the driver and the emulation).

Signed-off-by: Guolin Yang <gyang@vmware.com>
Signed-off-by: Shrikrishna Khare <skhare@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>