mtd: nand: omap: remove selection of BCH ecc-scheme via KConfig

With OMAP NAND driver updates, selection of ecc-scheme:
*DT enabled kernel*
 	depends on ti,nand-ecc-opt and ti,elm-id DT bindings.
*Non DT enabled kernel*
	depends on elm_dev and ecc-scheme passed along with platform-data
	from board file.

So, selection of ecc-scheme (BCH8 or BCH4) from KConfig can be removed

Signed-off-by: Pekon Gupta <pekon@ti.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>