Add a loop with timeout to make sure the iATU is really enabled before
subsequent config and I/O accesses.

[bhelgaas: split to separate patch, use dev_err() instead of dev_dbg()]
Signed-off-by: NJoao Pinto <jpinto@synopsys.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>