arm64/rockchip: Remove rk3328-dwc3 overlays

Not needed after
3c790abfba67 arm64/rk_dwc3: Remove RK3328 support
c45296f16f79 dwc3: Handle optional clocks

Differential Revision: https://reviews.freebsd.org/D37395
Sponsored by: Beckhoff Automation GmbH & Co. KG