ARM: dts: r8a7791: update PFC node name to pin-controller

The device trees for Renesas SoCs use either pfc or pin-controller as the
node name for the PFC device. This patch is intended to take a step towards
unifying the node name used as pin-controller which appears to be the more
generic of the two and thus more in keeping with the DT specs.

My analysis is that this is a user-visible change to the extent that kernel
logs, and sysfs entries change from e6060000.pfc and pfc@e6060000 to
e6060000.pin-controller and pin-controller@e6060000.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm/boot/dts/r8a7791.dtsi

@@ -562,7 +562,7 @@ i2c8: i2c@e6510000 {
 		status = "disabled";
 	};
 
-	pfc: pfc@e6060000 {
+	pfc: pin-controller@e6060000 {
 		compatible = "renesas,pfc-r8a7791";
 		reg = <0 0xe6060000 0 0x250>;
 	};