dt-bindings: clock: mediatek: add clock controllers of MT7988

Add various clock controllers found in the MT7988 SoC to existing
bindings (if applicable) and add files for the new ethwarp, mcusys
and xfi-pll clock controllers not previously present in any SoC.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/07e76a544ce4392bcb88e34d5480e99bb7994618.1702849494.git.daniel@makrotopia.org


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>