Convert CONFIG_CMD_IDE to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_IDE

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/digsy_mtc_defconfig b/configs/digsy_mtc_defconfig
index 85b7f85..da9cec8 100644
--- a/configs/digsy_mtc_defconfig
+++ b/configs/digsy_mtc_defconfig
@@ -11,6 +11,7 @@
 CONFIG_AUTOBOOT_PROMPT="autoboot in %d seconds\n"
 CONFIG_AUTOBOOT_DELAY_STR=" "
 CONFIG_LOOPW=y
+CONFIG_CMD_IDE=y
 CONFIG_CMD_USB=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y