RDMA/bnxt_re: Use ib_device_try_get()

There are a couple places in this driver running from a work queue that
need the ib_device to be registered. Instead of using a broken internal
bit rely on the new core code to guarantee device registration.

Link: https://lore.kernel.org/r/1584117207-2664-2-git-send-email-selvin.xavier@broadcom.com


Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>