ARMv8/PSCI: Fixup the device tree for PSCI

Set the enable-method in the cpu node to PSCI, and create device
node for PSCI, when PSCI was enabled.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/arch/arm/cpu/armv8/Makefile b/arch/arm/cpu/armv8/Makefile
index ee9e009..33e6db0 100644
--- a/arch/arm/cpu/armv8/Makefile
+++ b/arch/arm/cpu/armv8/Makefile
@@ -15,6 +15,7 @@
 obj-y	+= tlb.o
 obj-y	+= transition.o
 obj-y	+= fwcall.o
+obj-y	+= cpu-dt.o
 obj-$(CONFIG_ARMV8_SEC_FIRMWARE_SUPPORT) += sec_firmware.o sec_firmware_asm.o
 
 obj-$(CONFIG_FSL_LAYERSCAPE) += fsl-layerscape/