firewire: fw-sbp2: don't retry login or reconnect after unplug

firewire: fw-sbp2: don't retry login or reconnect after unplug

If a device is being unplugged while fw-sbp2 had a login or reconnect on
schedule, it would take about half a minute to shut the fw_unit down:

    Jan 27 18:34:54 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
    <unplug>
    Jan 27 18:34:59 stein firewire_sbp2: sbp2_scsi_abort
    Jan 27 18:34:59 stein scsi 25:0:0:0: Device offlined - not ready after error recovery
    Jan 27 18:35:01 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:06 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:12 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:17 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:22 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:27 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:32 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:32 stein firewire_sbp2: failed to login to fw2.0 LUN 0000
    Jan 27 18:35:32 stein firewire_sbp2: released fw2.0

After this patch, typically only a few seconds spent in __scsi_add_device
remain:

    Jan 27 19:05:50 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
    <unplug>
    Jan 27 19:05:56 stein firewire_sbp2: sbp2_scsi_abort
    Jan 27 19:05:56 stein scsi 33:0:0:0: Device offlined - not ready after error recovery
    Jan 27 19:05:56 stein firewire_sbp2: released fw2.0

The benefit of this is less noise in the syslog.  It furthermore avoids
a few wasted CPU cycles and needlessly prolonged lifetime of a few
driver objects.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Jarod Wilson <jwilson@redhat.com>