README: Reference nand monitor commands in U-Boot README

Reference nand monitor commands in U-Boot README

Signed-off-by: Karl O. Pinc <kop@meme.com>
diff --git a/README b/README
index 15596a7..aab3c2f 100644
--- a/README
+++ b/README
@@ -3880,6 +3880,7 @@
 protect - enable or disable FLASH write protection
 erase	- erase FLASH memory
 flinfo	- print FLASH memory information
+nand	- NAND memory operations (see doc/README.nand)
 bdinfo	- print Board Info structure
 iminfo	- print header information for application image
 coninfo - print console devices and informations