power: Add CONFIG_SPL_POWER_DOMAIN config

Add CONFIG_SPL_POWER_DOMAIN config entry.
Build drivers/power/domain if this config is selected.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/power/domain/Makefile b/drivers/power/domain/Makefile
index c7d7644..020eee2 100644
--- a/drivers/power/domain/Makefile
+++ b/drivers/power/domain/Makefile
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_POWER_DOMAIN) += power-domain-uclass.o
+obj-$(CONFIG_$(SPL_)POWER_DOMAIN) += power-domain-uclass.o
 obj-$(CONFIG_BCM6328_POWER_DOMAIN) += bcm6328-power-domain.o
 obj-$(CONFIG_SANDBOX_POWER_DOMAIN) += sandbox-power-domain.o
 obj-$(CONFIG_SANDBOX_POWER_DOMAIN) += sandbox-power-domain-test.o