wandboard: Print the board version in board_late_init()

wandboard: Print the board version in board_late_init()

Since CONFIG_DISPLAY_BOARDINFO_LATE is no longer used,  the checkboard()
function is no longer called.

As it is useful to print the board revision, print it inside
board_late_init() instead.

Also, to avoid GPIO errors related to using a GPIO without requesting it,
move the gpio_request(REV_DETECTION, "REV_DETECT") call prior to its
usage.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Heiko Schocher <hs@denx.de>