arm64: defconfig: Allow mt8173-based boards to boot from usb

Enable the option necessary to boot mt8173-based boards to boot from
usb devices, like its phy and the regulators needed to have proper
support.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
Link: https://lore.kernel.org/r/20210331090659.4169966-1-enric.balletbo@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>