scsi: device_handler: Return error pointer in scsi_dh_attached_handler_name()

scsi: device_handler: Return error pointer in scsi_dh_attached_handler_name()

If scsi_dh_attached_handler_name() fails to allocate the handler name,
dm-multipath (its only caller) assumes there is no attached device
handler, and sets the device up incorrectly. Return an error pointer
instead, so multipath can distinguish between failure, success where
there is no attached device handler, or when the path device is not a
SCSI device at all.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Link: https://patch.msgid.link/20251206010015.1595225-1-bmarzins@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>