SA queries SM for class port info when there is a LID_CHANGE event.

When a base lid is configured before fm is started ie when smlid is
not yet assigned, SA handles the LID_CHANGE event and tries query SM
with lid 0. This will cause an hang.

[ 1106.958820] INFO: task kworker/2:0:23 blocked for more than 120 seconds.
[ 1106.965082] Tainted: G O 4.12.0+ #1
[ 1106.969602] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
 this message.
[ 1106.977227] kworker/2:0 D 0 23 2 0x00000000
[ 1106.977250] Workqueue: infiniband update_ib_cpi [ib_core]
[ 1106.977261] Call Trace:
[ 1106.977273] __schedule+0x28e/0x860
[ 1106.977285] schedule+0x36/0x80
[ 1106.977298] schedule_timeout+0x1a3/0x2e0
[ 1106.977310] ? radix_tree_iter_tag_clear+0x1b/0x20
[ 1106.977322] ? idr_alloc+0x64/0x90
[ 1106.977334] wait_for_completion+0xe3/0x140
[ 1106.977347] ? wake_up_q+0x80/0x80
[ 1106.977369] update_ib_cpi+0x163/0x210 [ib_core]
[ 1106.977381] process_one_work+0x147/0x370
[ 1106.977394] worker_thread+0x4a/0x390
[ 1106.977406] kthread+0x109/0x140
[ 1106.977418] ? process_one_work+0x370/0x370
[ 1106.977430] ? kthread_park+0x60/0x60
[ 1106.977443] ret_from_fork+0x22/0x30

Always ensure a proper smlid is assigned before querying SM for cpi.

Fixes: ee1c60b1

 ("IB/SA: Modify SA to implicitly cache Class Port info")
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>