clk: mediatek: clk-pllfh: Export register/unregister/parse functions

These functions are used by the various MediaTek apmixed clock drivers
that may be built as modules: export the common functions used to parse
related devicetree properties, register and unregister the PLLFH clocks.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230206100105.861720-3-angelogioacchino.delregno@collabora.com


Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>