thunderbolt: Keep the parent runtime resumed for a while on device disconnect

commit b658eb9d upstream.

When doing device firmware upgrade the device will disconnect for a
while and then reconnect back. Keep the parent device (and the whole
domain) powered for a while so we don't need to runtime resume
immediately when the device is connected back after the device upgrade
completes.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>