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/configs/cm_fx6_defconfig b/configs/cm_fx6_defconfig
index dc587a6..a548d8f 100644
--- a/configs/cm_fx6_defconfig
+++ b/configs/cm_fx6_defconfig
@@ -35,6 +35,7 @@
 CONFIG_CMD_USB=y
 # CONFIG_CMD_FPGA is not set
 CONFIG_CMD_GPIO=y
+CONFIG_CMD_SATA=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_PING=y