dmaengine: idxd: fix missed completion on abort path

dmaengine: idxd: fix missed completion on abort path

Ming reported that with the abort path of the descriptor submission, there
can be a window where a completed descriptor can be missed to be completed
by the irq completion thread:

CPU A				CPU B
Submit (successful)

Submit (fail)
				irq_process_work_list() // empty

llist_abort_desc()
// remove all descs from pending list

				irq_process_pending_llist() // empty
				exit idxd_wq_thread() with no processing

Add opportunistic descriptor completion in the abort path in order to
remove the missed completion.

Fixes: 6b4b87f2c31a ("dmaengine: idxd: fix submission race window")
Reported-by: Ming Li <ming4.li@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163898288714.443911.16084982766671976640.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>