bnxt_en: Remove unnecessary assignment of return code

As part of converting error code in firmware message to standard
code, checking for firmware return code is removed in most of the
places. Remove the assignment of return code where the function
can directly return.

Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>