ARM64: dts: meson-axg: enable AP6255 wifi module

The Meson-AXG S400 board is shipped with AP6255 wifi module,
which is actually using the brcmfmac 43455 driver.

Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>