ARM64: dts: meson-axg: fix pwm_AO_cd compatible

The compatible in pwm_AO_cd is wrong and does not match anything.
Correct this with the correct compatible string

Fixes: 4a81e5dd ("ARM64: dts: meson-axg: add PWM DT info for Meson-Axg SoC")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>