powerpc/dts: don't fall back to fsl,pq3-gpio for fsl,mpc8572-gpio

While the handling of fsl,pq3-gpio and fsl,mpc8572-gpio is done in the
same driver and the two hardly differ, the latter controller needs a
workaround for an erratum in the gpio_get callback. To make this
difference more explicit remove fsl,pq3-gpio from the list of
compatibles for mpc8572 machines.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NScott Wood <scottwood@freescale.com>

arch/powerpc/boot/dts/fsl/mpc8536si-post.dtsi

@@ -172,7 +172,7 @@
 
 	/* mark compat w/8572 to get some erratum treatment */
 	gpio-controller@f000 {
-		compatible = "fsl,mpc8572-gpio", "fsl,pq3-gpio";
+		compatible = "fsl,mpc8572-gpio";
 	};
 
 	sata@18000 {

arch/powerpc/boot/dts/fsl/mpc8572si-post.dtsi

@@ -162,7 +162,7 @@
 /include/ "pq3-dma-1.dtsi"
 /include/ "pq3-gpio-0.dtsi"
 	gpio-controller@f000 {
-		compatible = "fsl,mpc8572-gpio", "fsl,pq3-gpio";
+		compatible = "fsl,mpc8572-gpio";
 	};
 
 	L2: l2-cache-controller@20000 {