bp->sriov_cfg is not defined when CONFIG_BNXT_SRIOV is not set.  Fix
it by adding a helper function bnxt_sriov_cfg() to handle the logic
with or without the config option.

Fixes: 46d08f55 ("bnxt_en: extend RTNL to VF check in devlink driver_reinit")
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/1637090770-22835-1-git-send-email-michael.chan@broadcom.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>