arm64: dts: qcom: gaokun3: Add Embedded Controller node

arm64: dts: qcom: gaokun3: Add Embedded Controller node

The Embedded Controller in the Huawei Matebook E Go is accessible on &i2c15
and provides battery and adapter status, port orientation status, as well
as HPD event notifications for two USB Type-C port, etc.

Add the EC to the device tree and describe the relationship among
the type-c connectors, role switches, orientation switches and the QMP
combo PHY.

Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250214180656.28599-4-mitltlatltl@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>