board: sifive: unmatched: reset USB hub, PCIe-USB bridge, and ULPI device in SPL

Ensure USB hub, PCIe-USB bridge, and ULPI device to be reset
even if the rebooting is without power-cycling.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>