ARM: davinci: da850-evm: use aemif platform driver in legacy mode

We now support board files in the aemif driver. Register a platform
device instead of using the handcrafted API in da850-evm.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>