mtd: nand: davinci: adjust DT properties to MTD generic

The properties davinci-ecc-mode, davinci-nand-use-bbt, davinci-nand-buswidth
are MTD generic. Correct names for them are: nand-ecc-mode, nand-on-flash-bbt,
nand-bus-width accordingly. So rename them in dts and documentation.

Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Taras Kondratiuk <taras@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>