PCI: pciehp: remove crit_sect mutex

The crit_sect mutex defined in struct controller is to serialize
hot-plug operations against multiple slots under the same bus. But,
since PCIe doesnstream port has only one slot at most, it is
meaningless and we don't need it.

Acked-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>