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/net2big_v2_defconfig b/configs/net2big_v2_defconfig
index ff222a1..ab8eb95 100644
--- a/configs/net2big_v2_defconfig
+++ b/configs/net2big_v2_defconfig
@@ -10,6 +10,7 @@
 CONFIG_SYS_PROMPT="2big2> "
 # CONFIG_CMD_IMLS is not set
 CONFIG_CMD_EEPROM=y
+CONFIG_CMD_IDE=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_SF=y
 CONFIG_CMD_I2C=y