arm64: dts: mediatek: Add missing xHCI clocks for mt8192 and mt8195

arm64: dts: mediatek: Add missing xHCI clocks for mt8192 and mt8195

The MediaTek xHCI dt-binding expects a specific order for the clocks,
but the mt8192 and mt8195 devicetrees were skipping some of the middle
clocks. These clocks are wired to the controller hardware but aren't
controllable.

Add the missing clocks as handles to fixed clocks, so that the clock
order is respected and the dtbs_check warnings are gone.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220708194314.56922-1-nfraprado@collabora.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>