Fix wrong counter check for proc_dir_entry in pci_proc_detach_device().

The pci_proc_detach_device() returns with -EBUSY before calling
remove_proc_entry() if the reference counter of proc_dir_entry is not
0. But this check is wrong and pci_proc_detach_device() always fails
because the reference counter of proc_dir_entry is initialized with 1
at creating time and decremented in remove_proc_entry(). This bug
cause strange behaviour as followings:

- Accessing /proc/bus/pci/XXXX/YY file after hot-removing pci adapter
  card causes kernel panic.

- Repeating hot-add/hot-remove of pci adapter card increases files
  with the same name under /proc/bus/pci/XXXX/ directory. For example:

    # pwd
    /proc/bus/pci/0002:09
    # ls
    01.0
    # for i in `seq 5`
    > do
    > echo 0 > /sys/bus/pci/slots/0009_0032/power
    > echo 1 > /sys/bus/pci/slots/0009_0032/power
    > done
    # ls
    01.0  01.0  01.0  01.0  01.0  01.0

The pci_proc_detach_device() should check if the reference counter is
not larger than 1 instead.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>