dm: Implement a CPU uclass

It is useful to be able to keep track of the available CPUs in a multi-CPU
system. This uclass is mostly intended for use with SMP systems.

The uclass provides methods for getting basic information about each CPU.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/cpu/Kconfig b/drivers/cpu/Kconfig
new file mode 100644
index 0000000..0d1424d
--- /dev/null
+++ b/drivers/cpu/Kconfig
@@ -0,0 +1,8 @@
+config CPU
+	bool "Enable CPU drivers using Driver Model"
+	help
+	  This allows drivers to be provided for CPUs and their type to be
+	  specified in the board's device tree. For boards which support
+	  multiple CPUs, then normally have to be set up in U-Boot so that
+	  they can work correctly in the OS. This provides a framework for
+	  finding out information about available CPUs and making changes.