The ssusb power domains currently don't list any clocks, despite
depending on some, and thus rely on the bootloader leaving the required
clocks on in order to work.

When booting with the upstream arm64 defconfig, the power domain
controller will defer probe until modules have loaded since it has an
indirect dependency on CONFIG_MTK_CMDQ, which is configured as a module.
However at the point where modules are loaded, unused clocks are also
disabled, causing the ssusb domains to fail to be enabled and
consequently the controller to fail probe:

mtk-power-controller 10006000.syscon:power-controller: /soc/syscon@10006000/power-controller/power-domain@4: failed to power on domain: -110
mtk-power-controller: probe of 10006000.syscon:power-controller failed with error -110

Add the missing clocks for the ssusb power domains so that they can
successfully probe without relying on the bootloader state.

Fixes: d9e43c1e ("arm64: dts: mt8186: Add power domains controller")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20240213-mt8186-ssusb-domain-clk-fix-v2-1-1f981d35f3fd@collabora.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>