ARM64: dts: meson-gxl: Add Ethernet PHY LEDS pins nodes

The Amlogic Meson GXL SoCs embeds an 10/100 Ethernet PHY, this patchs adds
the Link and Activity LEDs signals pins nodes.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>