bnxt_en: Do driver unregister cleanup in bnxt_init_one() failure path.

In the bnxt_init_one() failure path, if the driver has already called
firmware to register the driver, it is not undoing the driver
registration.  Add this missing step to unregister for correctness,
so that the firmware knows that the driver has unloaded.

Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>