usb: host: ehci-sched: Remove ununsed function tt_start_uframe()

commit b35c5009 ("USB: EHCI: create per-TT bandwidth tables")
left behind this, remove it.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200909134405.34036-1-yuehaibing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>