ipr: Reset in task context

The pci_set_pcie_reset_state has changed semantics to not be callable
from interrupt context, so change ipr's usage of the API to comply with
this change by ensuring this occurs from a workqueue.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Reviewed-by: Daniel Kreling <kreling@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>