MTD: fix all kernel-doc warnings

Fix all kernel-doc warnings in MTD headers and source files:
- add some missing struct fields;
- correct some function parameter names;
- use kernel-doc format for function doc. headers;
- nand_ecc.c contains only exported interfaces, no internal ones;

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

Documentation/DocBook/mtdnand.tmpl

@@ -1295,7 +1295,9 @@ in this page</entry>
      </para>
 !Idrivers/mtd/nand/nand_base.c
 !Idrivers/mtd/nand/nand_bbt.c
-!Idrivers/mtd/nand/nand_ecc.c
+<!-- No internal functions for kernel-doc:
+X!Idrivers/mtd/nand/nand_ecc.c
+-->
   </chapter>
 
   <chapter id="credits">