IB/rdmavt: Add device structure allocation

This patch adds rdmavt device structure allocation in rdamvt. The
ib_device alloc is now done in rdmavt instead of the driver. Drivers
need to tell rdmavt the number of ports when calling.

A side of effect of this patch is fixing a bug with port initialization
where the device structure port array was allocated over top of an
existing one.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>