Setup the emc pins used by external memory devices and add
configuration for the devices found on the EA4357 devkit.

The EA4357 devkit has a NOR Flash attached to chip select 0
and a D-type flip-flop used for LEDs on chip select 2.
Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>