pciehp: move msleep after power off

According to the PCI Express specification, we must wait for at least
1 second after turning power off before taking any action that relies
on power having been removed from the slot/adapter. For this, current
pciehp wait for 1 second after issuing the power off command in
hpc_power_off_slot() function. But waiting for 1 second in
hpc_power_off_slot() can make pciehp probing slow-down because pciehp
probe code calls hpc_power_off_slot() if the slot is not occupied just
in case. We don't need to wait for 1 second at the pciehp probe time
because there is no action on that empty slot. So move 1 second wait
from hpc_power_off_slot() to the caller of hpc_power_off_slot().

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>