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/sheevaplug_defconfig b/configs/sheevaplug_defconfig
index fa99d515..80cc62e 100644
--- a/configs/sheevaplug_defconfig
+++ b/configs/sheevaplug_defconfig
@@ -7,6 +7,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set
+CONFIG_CMD_IDE=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MMC=y
 CONFIG_CMD_NAND=y