[POWERPC] pseries: Print PCI slot location code on failure

The PCI error recovery code will printk diagnostic info when
a PCI error event occurs. Change the messages to include the slot
location code, which is how most sysadmins will know the device.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>