PCI hotplug: ioremap balanced with iounmap

1. ioremap must be balanced by an iounmap and failing to do so can
   result in a memory leak.
2. Handle return value correctly

Tested (compilation only) with:
- allmodconfig

Signed-off-by: Amol Lad <amol@verismonetworks.com>
Cc: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>