usb: xhci-mtk: use first-fit for LS/FS

Use first-fit instead of best-fit for LS/FS devices under TT,
we found that best-fit will consume more bandwidth for some
cases.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20210507021127.54717-4-chunfeng.yun@mediatek.com


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