arm64: dts: exynos: gs101-pixel-common: add node for s2mpg10 / clock

arm64: dts: exynos: gs101-pixel-common: add node for s2mpg10 / clock

On Pixel 6 (and Pro), a Samsung S2MPG10 is used as main PMIC, which
contains the following functional blocks:
    * common / speedy interface
    * regulators
    * 3 clock outputs
    * RTC
    * power meters

This change adds a node for the clock outputs which are used as inputs
as follows:
* RTC clock for AP
* GNSS receiver, WLAN, Bluetooth
* vibrator, modem

The names have been chosen to match the schematic.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>