drivers/pci/hotplug: Add missing pci_dev_get

drivers/pci/hotplug: Add missing pci_dev_get

pci_get_slot does a pci_dev_get, so pci_dev_put needs to be called in an
error case.

An alterative would be to move the test_and_set_bit before the call to
pci_get_slot.

The problem was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
local idexpression *n;
statement S1,S2;
expression E,E1;
expression *ptr != NULL;
type T,T1;
@@

(
if (!(n = pci_get_slot(...))) S1
|
n = pci_get_slot(...)
)
<... when != pci_dev_put(n)
    when != if (...) { <+... pci_dev_put(n) ...+> }
    when != true !n  || ...
    when != n = (T)E
    when != E = n
if (!n || ...) S2
...>
(
  return \(0\|<+...n...+>\|ptr\);
|
+ pci_dev_put(n);
return ...;
|
pci_dev_put(n);
|
n = (T1)E1
|
E1 = n
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>