The test clock isn't in the bindings and apparently it's not used by
anyone upstream.  Remove it.
Suggested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lkml.kernel.org/r/20200203103049.v4.9.I6d5276b768f6593053be036a3e70cce298d39f0c@changeidSigned-off-by: Stephen Boyd <sboyd@kernel.org>