clk: mediatek: mt7622: Convert to platform driver and simple probe

Convert the MT7622 topckgen and pericfg clock drivers to platform
drivers and use the simple probe mechanism. This also allows to
build these clocks as modules.

Thanks to the conversion, more error handling was added to the clocks
registration.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230306140543.1813621-28-angelogioacchino.delregno@collabora.com


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