nand: Add support for unlock.invert

NAND unlock command allows an invert bit to be set to unlock all but
the selected page range.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
[scottwood@freescale.com: updated docs and added comment about invert bit]
Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/doc/README.nand b/doc/README.nand
index 1602b5e..c130189 100644
--- a/doc/README.nand
+++ b/doc/README.nand
@@ -228,6 +228,8 @@
   "nand unlock [offset] [size]"
   unlock consecutive area (can be called multiple times for different areas)
 
+  "nand unlock.allexcept [offset] [size]"
+  unlock all except specified consecutive area
 
 I have tested the code with board containing 128MiB NAND large page chips
 and 32MiB small page chips.