arm64: dts: meson: a1: add definitions for meson PWM

arm64: dts: meson: a1: add definitions for meson PWM

The chip has 3 dual-channel PWM modules PWM_AB, PWM_CD, PWM_EF those
can be connected to various digital I/O pins.

Each of 6 PWM is driven by individually selected clock parent and
8-bit divider. The PWM signal is generated using two 16-bit counters.

Signed-off-by: George Stark <gnstark@salutedevices.com>
Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240710234116.2370655-4-gnstark@salutedevices.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>