Convert CONFIG_CMD_SATA to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_SATA

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/powerpc/cpu/mpc83xx/Kconfig b/arch/powerpc/cpu/mpc83xx/Kconfig
index 0772b7c..cdd21a2 100644
--- a/arch/powerpc/cpu/mpc83xx/Kconfig
+++ b/arch/powerpc/cpu/mpc83xx/Kconfig
@@ -54,6 +54,7 @@
 config TARGET_MPC837XEMDS
 	bool "Support MPC837XEMDS"
 	select BOARD_EARLY_INIT_F
+	imply CMD_SATA
 
 config TARGET_MPC837XERDB
 	bool "Support MPC837XERDB"