Return the exactly delay time given by root hub descriptor,
this helps to reduce resume time etc.

Due to the root hub descriptor is usually provided by the host
controller driver, if there is compatibility for a root hub,
we can fix it easily without affect other root hub
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NChunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1618017645-12259-1-git-send-email-chunfeng.yun@mediatek.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>