scsi: lpfc: fix block guard enablement on SLI3 adapters

Since f44ac12f, BG enablement is tracked with the LPFC_SLI3_BG_ENABLED
bit, which is set in lpfc_get_cfgparam before lpfc_sli_config_sli_port() is
called. The bit shouldn't be cleared before checking the feature.  Based on
problem analysis by David Bond.

Fixes: f44ac12f "scsi: lpfc: Memory allocation error during driver start-up on power8"
Tested-by: David Bond <dbond@suse.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Cc: stable@vger.kernel.org # 4.17.x
Cc: stable@vger.kernel.org # 4.18.x
Cc: stable@vger.kernel.org # 4.19.x
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>