dt-bindings: pinctrl: meson: Add drive-strength-microamp property

Add optional drive-strength-microamp property
Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/meson,pinctrl.txt

@@ -51,6 +51,10 @@ Configuration nodes support the generic properties "bias-disable",
 "bias-pull-up" and "bias-pull-down", described in file
 pinctrl-bindings.txt
 
+Optional properties :
+ - drive-strength-microamp: Drive strength for the specified pins in uA.
+			    This property is only valid for G12A and newer.
+
 === Example ===
 
 	pinctrl: pinctrl@c1109880 {