toradex: common: Use SETTINGS_R event to read toradex config block

Use SETTINGS_R event to read toradex config block and checkboard()
to print board info.

Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com> # Verdin iMX8M Plus
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>