bnxt_en: Check devlink allocation and registration status

devlink is a software interface that doesn't depend on any hardware
capabilities. The failure in SW means memory issues, wrong parameters,
programmer error e.t.c.

Like any other such interface in the kernel, the returned status of
devlink APIs should be checked and propagated further and not ignored.

Fixes: 4ab0c6a8

 ("bnxt_en: add support to enable VF-representors")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>