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>
diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
index 2a163e4..dd438ca 100644
--- a/drivers/mtd/nand/nand_ecc.c
+++ b/drivers/mtd/nand/nand_ecc.c
@@ -65,8 +65,7 @@
 };
 
 /**
- * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code
- *			for 256 byte block
+ * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
  * @mtd:	MTD block structure
  * @dat:	raw data
  * @ecc_code:	buffer for ECC