usb: mtu3: restore HS function when set SS/SSP

Due to HS function is disabled when set as FS, need restore
it when set as SS/SSP.

Fixes: dc4c1aa7 ("usb: mtu3: add ->udc_set_speed()")
Cc: stable@vger.kernel.org
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1628836253-7432-1-git-send-email-chunfeng.yun@mediatek.com


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