dt-bindings: phy: amlogic,meson-axg-mipi-pcie-analog: drop text about parent syscon...

dt-bindings: phy: amlogic,meson-axg-mipi-pcie-analog: drop text about parent syscon and drop example

Since this bindings is referred from amlogic,meson-gx-hhi-sysctrl.yaml, drop the now
useless description about the parent node and also drop the unnecessary example.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20231124-amlogic-v6-4-upstream-dsi-ccf-vim3-v9-3-95256ed139e6@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>