bnx2: Wait for in-flight DMA to complete at probe stage

In-flight DMA from 1st kernel could continue going in kdump kernel.
New io-page table has been created before bnx2 does reset at open stage.
We have to wait for the in-flight DMA to complete to avoid it look up
into the newly created io-page table at probe stage.

Suggested-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>