clk: mediatek: add clock driver support for MediaTek MT7986 SoC

This patch adds clock driver support for MediaTek MT7986 SoC

Reviewed-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>