PCI: pciehp: Fix wait time in timeout message

When we warned about a timeout on a hotplug command, we previously printed
the time between calls to pcie_write_cmd(), without accounting for any time
spent actually waiting.  Consider this sequence:

  pcie_write_cmd
    write SLTCTL
    cmd_started = jiffies          # T1

  pcie_write_cmd
    pcie_wait_cmd
      now = jiffies                # T2
      wait_event_timeout           # we may wait here
      if (timeout)
        ctrl_info("Timeout on command issued %u msec ago",
                  jiffies_to_msecs(now - cmd_started))

We previously printed (T2 - T1), but that doesn't include the time spent in
wait_event_timeout().

Fix this by using the current jiffies value, not the one cached before
calling wait_event_timeout().

[bhelgaas: changelog, use current jiffies instead of adding timeout]
Fixes: 40b96083 ("PCI: pciehp: Compute timeout from hotplug command start time")
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>