RDMA/bnxt_re: Use driver_unregister and unregistration API

RDMA/bnxt_re: Use driver_unregister and unregistration API

Using the new unregister APIs provided by the core.  Provide the
dealloc_driver hook for the core to callback at the time of device
un-registration.

bnxt_re VF resources are created by the corresponding PF driver.  During
ib_unregister_driver, PF might get removed before VF and this could cause
failure when VFs are removed. Driver is explicitly queuing the removal of
VF devices before calling ib_unregister_driver.

Link: https://lore.kernel.org/r/1582731932-26574-3-git-send-email-selvin.xavier@broadcom.com
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>