arm64: dts: meson-gxl-s905x-khadas-vim: fix gpio-keys-polled node

Fix DTC warnings:

arch/arm/dts/meson-gxl-s905x-khadas-vim.dtb: Warning (avoid_unnecessary_addr_size):
   /gpio-keys-polled: unnecessary #address-cells/#size-cells
      without "ranges" or child "reg" property

Fixes: e15d2774 ("ARM64: dts: meson-gxl: add support for the Khadas VIM board")
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>