agp: amd64, fix pci reference leaks

Stanse found pci reference leaks in uli_agp_init and nforce3_agp_init
initialization functions.

The PCI devices are bridges, so it's not critical, but still worth fixing.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>