clk: mediatek: mt8135-apmixedsys: Convert to platform_driver and module

Convert apmixedsys clocks to be a platform driver; while at it, also
add necessary error handling to the probe function, add a remove
callback and provide a MODULE_DESCRIPTION().

This driver is now compatible with an eventual module build.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230306140543.1813621-53-angelogioacchino.delregno@collabora.com


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