clk: mediatek: mux: Reverse check for existing clk to reduce nesting level

The clk registration code here currently does:

    if (IS_ERR_OR_NULL(clk_data->clks[mux->id])) {
            ... do clk registration ...
    }

This extra level of nesting wastes screen real estate.

Reduce the nesting level by reversing the conditional shown above.
Other than that, functionality is not changed.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220208124034.414635-24-wenst@chromium.org


Reviewed-by: Chun-Jie Chen <chun-jie.chen@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>