clk: mediatek: add clock support for MT7622 SoC

Add all supported clocks exported from every susbystem found on MT7622 SoC
such as topckgen, apmixedsys, infracfg, pericfg , pciessys, ssusbsys,
ethsys and audsys.

Signed-off-by: Chen Zhong <chen.zhong@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>