Add dt schema documentation and clock IDs for the High Speed Interface
2 (HSI2) clock management unit. This CMU feeds high speed interfaces
such as PCIe and UFS.

[AD: * keep CMUs in google,gs101.h sorted alphabetically
     * resolve minor merge conflicts in google,gs101-clock.yaml
     * s/ufs_embd/ufs    s/mmc_card/mmc
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20240429-hsi0-gs101-v3-1-f233be0a2455@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>