clk: qcom: camcc-sc7180: get rid of the test clock

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: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211228045415.20543-6-dmitry.baryshkov@linaro.org