imls: Add support to list images in NAND device

This patch adds support to list images in NAND flash through imls

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
diff --git a/README b/README
index d8cb394..0070694 100644
--- a/README
+++ b/README
@@ -842,7 +842,8 @@
 		CONFIG_CMD_I2C		* I2C serial bus support
 		CONFIG_CMD_IDE		* IDE harddisk support
 		CONFIG_CMD_IMI		  iminfo
-		CONFIG_CMD_IMLS		  List all found images
+		CONFIG_CMD_IMLS		  List all images found in NOR flash
+		CONFIG_CMD_IMLS_NAND	  List all images found in NAND flash
 		CONFIG_CMD_IMMAP	* IMMR dump support
 		CONFIG_CMD_IMPORTENV	* import an environment
 		CONFIG_CMD_INI		* import data from an ini file into the env