ARM: dts: move the pwm_ab and pwm_cd nodes to meson.dtsi

According to the vendor kernel sources these also exist (at the same
address) on Meson6 and Meson8. This can be found by running
$ grep -R "define PWM_PWM_[A-D]" arch/arm/
in the Amlogic GPL kernel tree (arm-src-kernel-2015-01-15-321cfb5a46).
pwm_ef does not seem to exist on older SoCs, so we keep it in
meson8b.dtsi for now.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>