README: davinci: update the documentation for DaVinci

The DM* family of SOCs is no longer supported. We now support the
omap-l138 lcdk board and Lego EV3 platform. Reflect those changes
in the README.

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