dt-bindings: pwm: Update bindings for the Meson G12A Family

Update the doc to explicitly support Meson G12A Family.
The 2 first (A & B) AO PWM uses different clock source than the last 2
(C & D) AO PWM modules, thus we need to differentiate them.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-meson.txt

@@ -7,6 +7,9 @@ Required properties:
                          or "amlogic,meson-gxbb-ao-pwm"
                          or "amlogic,meson-axg-ee-pwm"
                          or "amlogic,meson-axg-ao-pwm"
+                         or "amlogic,meson-g12a-ee-pwm"
+                         or "amlogic,meson-g12a-ao-pwm-ab"
+                         or "amlogic,meson-g12a-ao-pwm-cd"
 - #pwm-cells: Should be 3. See pwm.txt in this directory for a description of
   the cells format.