PCI: Fix reference counting bug

pci_get_subsys() will decrement the reference count of the device that
it starts searching from.  Unfortunately, the pci_find_device() interface
will already have decremented the reference count of the device earlier,
so the device will end up losing all reference counts and be freed.

We can fix this by incrementing the reference count of the device to
start searching from before calling pci_get_subsys().

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>