In the bindings that landed for the gpucc we require that the XO clock
(one possible parent of the gpucc) be listed.  The code doesn't use
this yet--this is just to allow us to move toward the day when it does
use it.  What the code does do today is to hardcode the parent name to
"bi_tcxo".  That's all well and good.

...but the example in the bindings shows this clock mapping to the
clock "xo_board".  On the current sdm845.dtsi file the "xo_board"
clock is a fixed clock with an output name of "xo_board".  The clock
with the name "bi_tcxo" is actually provided by the RPMh Clock
Controller.  Presumably that's the one that was wanted.

Let's update the example to make this clearer.

Fixes: e431c921 ("dt-bindings: clock: Introduce QCOM Graphics clock bindings")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>