PCI: xgene: Fix double free on init error

The "port" variable was allocated with devm_kzalloc() so if we free it with
kfree() it will be freed twice.  Also I changed it to propogate the error
from devm_ioremap_resource() instead of returning -ENOMEM.

Fixes: c5d46039 ("PCI: Add MCFG quirks for X-Gene host controller")
Also-posted-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Tanmay Inamdar <tinamdar@apm.com>