Rename SPL_POWER_SUPPORT to SPL_POWER

Rename this option so that CONFIG_IS_ENABLED can be used with it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/doc/README.SPL b/doc/README.SPL
index 2beb6d8..005f038 100644
--- a/doc/README.SPL
+++ b/doc/README.SPL
@@ -56,7 +56,7 @@
 CONFIG_SPL_FS_FAT (fs/fat/libfat.o)
 CONFIG_SPL_FS_EXT4
 CONFIG_SPL_LIBGENERIC_SUPPORT (lib/libgeneric.o)
-CONFIG_SPL_POWER_SUPPORT (drivers/power/libpower.o)
+CONFIG_SPL_POWER (drivers/power/libpower.o)
 CONFIG_SPL_NAND_SUPPORT (drivers/mtd/nand/raw/libnand.o)
 CONFIG_SPL_DRIVERS_MISC_SUPPORT (drivers/misc)
 CONFIG_SPL_DMA (drivers/dma/libdma.o)