Use of_property_read_bool to check for the existence of a property.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2,x;
@@
-	if (of_get_property(e1,e2,NULL))
-		x = true;
-	else
-		x = false;
+	x = of_property_read_bool(e1,e2);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>