arm64: dts: meson: a1: change uart compatible string

In the current implementation, the meson-a1 configuration incorporates a
unique compatibility tag "amlogic,meson-a1-uart' within the meson-uart
driver due to its usage of the new console device name "ttyS".
Consequently, the previous compatibility tag designated for the
'amlogic,meson-gx-uart' configuration has become obsolete and is no
longer relevant to the current setup.

Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230705181833.16137-8-ddrokosov@sberdevices.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>