mtd: add new fields to nand_flash_dev{}

As time goes on, we begin to meet the situation that we can not get enough
information from some nand chips's id data. Take some Toshiba's nand chips
for example. I have 4 Toshiba's nand chips in my hand:
	TC58NVG2S0F, TC58NVG3S0F, TC58NVG5D2, TC58NVG6D2

When we read these chips' datasheets, we will get the geometry of these chips:
	TC58NVG2S0F : 4096 + 224
	TC58NVG3S0F : 4096 + 232
	TC58NVG5D2  : 8192 + 640
	TC58NVG6D2  : 8192 + 640

But we can not parse out the correct oob size for these chips from the id data.

This patch adds some new fields to the nand_flash_dev{}:
  @id_len: the valid length of the id data. See the comments in
           nand_id_has_period()
  @oobsize: the oob size.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Reviewed-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/nand.h

@@ -588,6 +588,8 @@ struct nand_chip {
  * @chipsize: total chip size in MiB
  * @erasesize: eraseblock size in bytes (determined from the extended ID if 0)
  * @options: stores various chip bit options
+ * @id_len: The valid length of the @id.
+ * @oobsize: OOB size
  */
 struct nand_flash_dev {
 	char *name;
@@ -602,6 +604,8 @@ struct nand_flash_dev {
 	unsigned int chipsize;
 	unsigned int erasesize;
 	unsigned int options;
+	uint16_t id_len;
+	uint16_t oobsize;
 };
 
 /**