The "simple" OF glue layer for the Designware USB3 core enables
all refernced clocks. These need to be need to be implemented
otherwise the driver fails to probe. A dummy implementation
that simply returns success is sufficient since the RK3399 comes
out of reset with all clock gates open.
Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
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