uas: fix error handling during scsi_scan()

intfdata is set only after scsi_scan(). uas_pre_reset() however
needs intfdata to be valid and will follow the NULL pointer
killing khubd. intfdata must be preemptively set before the
host is registered and undone in the error case.

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>