udoo-neo: Do not print devicetree model

udoo-neo: Do not print devicetree model

The udoo_neo_defconfig target supports several board variants.
All of these variants use the imx6sx-udoo-neo-basic devicetree in U-Boot.

Currently, the devicetree model as well as the board variant name
are shown:

...
Model: UDOO Neo Basic
Board: UDOO Neo FULL
...

Printing the devicetree model that is used internally by U-Boot
may confuse users.

Unselect the CONFIG_DISPLAY_BOARDINFO option and move the board printing
inside board_init() so that only the real board name that is detected
in run-time is printed.

Signed-off-by: Fabio Estevam <festevam@gmail.com>