IB/srpt: Fix wait list processing

Since the wait list is not protected against concurrent access
it must be processed from the context of the completion handler.
Replace the wait list processing code in the IB CM RTU callback
handler by code that triggers a completion handler. This patch
fixes the following rare crash:

WARNING: CPU: 2 PID: 78656 at lib/list_debug.c:53 __list_del_entry+0x67/0xd0()
list_del corruption, ffff88041ae404b8->next is LIST_POISON1 (dead000000000100)
Call Trace:
 [<ffffffff81251c6b>] dump_stack+0x4f/0x74
 [<ffffffff810574ab>] warn_slowpath_common+0x8b/0xd0
 [<ffffffff81057591>] warn_slowpath_fmt+0x41/0x70
 [<ffffffff8126f007>] __list_del_entry+0x67/0xd0
 [<ffffffff8126f081>] list_del+0x11/0x40
 [<ffffffffa0265242>] srpt_cm_handler+0x172/0x1a4 [ib_srpt]
 [<ffffffffa0370370>] cm_process_work+0x20/0xf0 [ib_cm]
 [<ffffffffa0370dae>] cm_establish_handler+0xbe/0x110 [ib_cm]
 [<ffffffffa03733e7>] cm_work_handler+0x67/0xd0 [ib_cm]
 [<ffffffff8107184d>] process_one_work+0x1bd/0x460
 [<ffffffff81073148>] worker_thread+0x118/0x420
 [<ffffffff81078444>] kthread+0xe4/0x100
 [<ffffffff8151caff>] ret_from_fork+0x3f/0x70

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Estrin <alex.estrin@intel.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>