arm64: dts: meson: add watchdog to g12-common dtsi

G12 vendor kernels show the watchdog on the same address as AXG
so add the node to meson-g12-common.dtsi. GX boards inherit the
same from meson-gx.dtsi.

v2 fix typo in node name (s/wtd/wdt)

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20201101021012.24519-1-christianshewitt@gmail.com