scsi: ibmvfc: Set default timeout to avoid crash during migration

While testing live partition mobility, we have observed occasional crashes
of the Linux partition. What we've seen is that during the live migration,
for specific configurations with large amounts of memory, slow network
links, and workloads that are changing memory a lot, the partition can end
up being suspended for 30 seconds or longer. This resulted in the following
scenario:

CPU 0                          CPU 1
-------------------------------  ----------------------------------
scsi_queue_rq                    migration_store
 -> blk_mq_start_request          -> rtas_ibm_suspend_me
  -> blk_add_timer                 -> on_each_cpu(rtas_percpu_suspend_me
              _______________________________________V
             |
             V
    -> IPI from CPU 1
     -> rtas_percpu_suspend_me
                                     -> __rtas_suspend_last_cpu

-- Linux partition suspended for > 30 seconds --
                                   ...