RDMA/bnxt_re: Use auxiliary driver interface

Use auxiliary driver interface for driver load, unload ROCE driver.
The driver does not need to register the interface using the netdev
notifier anymore. Removed the bnxt_re_dev_list which is not needed.
Currently probe, remove and shutdown ops have been implemented for
the auxiliary device.
Also remove exccessve validation checks for rdev.

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Reviewed-by: Selvin Xavier <selvin.xavier@broadcom.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>