agp: remove unnecessary pci_dev_put

pci_get_class implicitly does a pci_dev_put on its second argument, so
pci_dev_put is only needed if there is a break out of the loop.

The semantic match detecting this problem is as follows:

// <smpl>
@@
expression dev;
expression E;
@@

* pci_dev_put(dev)
  ... when != dev = E
(
* pci_get_device(...,dev)
|
* pci_get_device_reverse(...,dev)
|
* pci_get_subsys(...,dev)
|
* pci_get_class(...,dev)
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>