mtd: nand: davinci: reuse driver for Keystone arch

The Keystone arch has compatible nand device, so reuse it.
In case with Keystone it depends on TI_AEMIF because AEMIF
driver is responsible to set timings.

See http://www.ti.com/lit/ug/sprugz3a/sprugz3a.pdf

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>