clk: mediatek: mt8173: Migrate to platform driver and common probe

This driver is using CLK_OF_DECLARE() for all clocks: while this
definitely works, it's not preferred as this makes it impossible
to compile non boot critical clock drivers as modules and to take
advantage of clock controller Runtime PM.

As a preparation for a larger cleanup, migrate all of the clock
controller drivers for MT8173 to platform_driver and use the
common mtk_clk_simple_probe() where possible; while at it, also
add proper error handling to the various probe functions.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230120092053.182923-9-angelogioacchino.delregno@collabora.com
Tested-by: Mingming Su <mingming.su@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>