ARM: mvebu: add CA9 MPcore SoC Controller node

The CA9 MPcore SoC Control block is a set of registers that allows to
configure certain internal aspects of the core blocks of the SoC
(Cortex-A9, L2 cache controller, etc.). In most cases, the default
values are fine so they aren't many reasons to touch those registers,
but there is one exception: to support cpuidle on Armada 38x, we need
to modify the value of the CA9 MPcore Reset Control register.

Therefore, this commit adds a new Device Tree binding for this
hardware block, and uses this new binding for the Armada 38x Device
Tree file.

Signed-off-by: Gregory CLEMENT <[e-mail]>
Signed-off-by: Thomas Petazzoni <[e-mail]>
Cc: [e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Jason Cooper <[e-mail]>

Documentation/devicetree/bindings/arm/armada-380-mpcore-soc-ctrl.txt

···
+Marvell Armada 38x CA9 MPcore SoC Controller
+============================================
+
+Required properties:
+
+- compatible: Should be "marvell,armada-380-mpcore-soc-ctrl".
+
+- reg: should be the register base and length as documented in the
+  datasheet for the CA9 MPcore SoC Control registers
+
+mpcore-soc-ctrl@20d20 {
+	compatible = "marvell,armada-380-mpcore-soc-ctrl";
+	reg = <0x20d20 0x6c>;
+};

arch/arm/boot/dts/armada-38x.dtsi

···
 				reg = <0x20800 0x10>;
 			};
 
+			mpcore-soc-ctrl@20d20 {
+				compatible = "marvell,armada-380-mpcore-soc-ctrl";
+				reg = <0x20d20 0x6c>;
+			};
+
 			coherency-fabric@21010 {
 				compatible = "marvell,armada-380-coherency-fabric";
 				reg = <0x21010 0x1c>;