arm64: dts: mediatek: mt8186: fix VENC power domain clocks

arm64: dts: mediatek: mt8186: fix VENC power domain clocks

The larb clock is in fact a subsys clock, so it must be prefixed by
'subsys-' to be correctly identified in the driver.

Fixes: d9e43c1e7a38 ("arm64: dts: mt8186: Add power domains controller")
Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20231228113245.174706-6-eugen.hristev@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>