pcifront: fix PCI reference leak

pcifront: fix PCI reference leak

Stanse found that when pdev is found and has no driver a reference is
leaked in pcifront_common_process. So add pci_dev_put there. For the
pdev == NULL case, pci_dev_put(NULL) is fine.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
From: Jiri Slaby <jslaby@suse.cz>
Subject: pcifront: fix potential NULL dereference

Milton spotted that we dereference NULL in one fail path in
pcifront_common_process. Fix that by using different device to print
out an error.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Milton Miller <miltonm@bga.com>
Signed-off-by: Jan Beulich <jbeulich@novell.com>