arm64: dts: meson: add missing gxl rng clock

The peripheral clock of the RNG is missing for gxl while it is present
for gxbb.

Fixes: 1b3f6d14 ("ARM64: dts: meson-gx: add clock CLKID_RNG0 to hwrng node")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20200617125346.1163527-1-jbrunet@baylibre.com