scsi: lpfc: Honor module parameter lpfc_use_adisc

scsi: lpfc: Honor module parameter lpfc_use_adisc

The initial lpfc_desc_set_adisc implementation in commit
dea3101e0a5c ("lpfc: add Emulex FC driver version 8.0.28") enabled ADISC if

	cfg_use_adisc && RSCN_MODE && FCP_2_DEVICE

In commit 92d7f7b0cde3 ("[SCSI] lpfc: NPIV: add NPIV support on top of
SLI-3") this changed to

	(cfg_use_adisc && RSC_MODE) || FCP_2_DEVICE

and later in commit ffc954936b13 ("[SCSI] lpfc 8.3.13: FC Discovery Fixes
and enhancements.") to

	(cfg_use_adisc && RSC_MODE) || (FCP_2_DEVICE && FCP_TARGET)

A customer reports that after a devloss, an ADISC failure is logged. It
turns out the ADISC flag is set even the user explicitly set lpfc_use_adisc
= 0.

[Sat Dec 22 22:55:58 2018] lpfc 0000:82:00.0: 2:(0):0203 Devloss timeout on WWPN 50:01:43:80:12:8e:40:20 NPort x05df00 Data: x82000000 x8 xa
[Sat Dec 22 23:08:20 2018] lpfc 0000:82:00.0: 2:(0):2755 ADISC failure DID:05DF00 Status:x9/x70000

[mkp: fixed Hannes' email]

Fixes: 92d7f7b0cde3 ("[SCSI] lpfc: NPIV: add NPIV support on top of SLI-3")
Cc: Dick Kennedy <dick.kennedy@broadcom.com>
Cc: James Smart <james.smart@broadcom.com>
Link: https://lore.kernel.org/r/20191022072112.132268-1-dwagner@suse.de
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>