mtd: davinci_nand: cmdlinepart uses MTD IDs

Remove some legacy code from the davinci_nand driver, which made
cmdlinepart ignore the the MTD ID passed to it.  Boards can have
multiple NAND chips, and some do (like the DM357 EVM), so this
dated hack is undesirable.

Correct labels are like "davinci_nand.0" (for chipselect 0).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>