Add a power domain framework/uclass

Many SoCs allow power to be applied to or removed from portions of the SoC
(power domains). This may be used to save power. This API provides the
means to control such power management hardware.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/Makefile b/test/dm/Makefile
index cad3374..1885e17 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -24,6 +24,7 @@
 obj-$(CONFIG_DM_MAILBOX) += mailbox.o
 obj-$(CONFIG_DM_MMC) += mmc.o
 obj-$(CONFIG_DM_PCI) += pci.o
+obj-$(CONFIG_POWER_DOMAIN) += power-domain.o
 obj-$(CONFIG_RAM) += ram.o
 obj-y += regmap.o
 obj-$(CONFIG_REMOTEPROC) += remoteproc.o