mtd: cmdlinepart: update /proc/mtd comment

/proc/mtd doesn't contain the mtd-id of the device, but the part name from the
command line. This corrects what I believe is an obsolete comment from commit
a0ee24a03b1c06813c814b9f70946c8984752f01.

Signed-off-by: Christopher Cordahi <[e-mail]>
Cc: Philip Rakity <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>

drivers/mtd/cmdlinepart.c

···
  *
  * mtdparts=<mtddef>[;<mtddef]
  * <mtddef>  := <mtd-id>:<partdef>[,<partdef>]
- *              where <mtd-id> is the name from the "cat /proc/mtd" command
  * <partdef> := <size>[@<offset>][<name>][ro][lk]
  * <mtd-id>  := unique name used in mapping driver/device (mtd->name)
  * <size>    := standard linux memsize OR "-" to denote all remaining space
···
  *              if omitted the part will immediately follow the previous part
  *              or 0 if the first part
  * <name>    := '(' NAME ')'
+ *              NAME will appear in /proc/mtd
  *
  * <size> and <offset> can be specified such that the parts are out of order
  * in physical memory and may even overlap.