clk: mediatek: mt8167: Move apmixedsys as platform_driver in new file

In preparation for migrating all other MT8167 clocks to the common
mtk_clk_simple_probe(), move apmixedsys clocks to a different file.
While at it, also migrate away from the legacy CLK_OF_DECLARE and
convert this clock driver to be a platform_driver instead.

During the conversion, error handling was added to the apmixedsys
probe function.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230306140543.1813621-17-angelogioacchino.delregno@collabora.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>