configs: imx8mn_bsh_smm_s2: Use nand_base ident for nand identification

The board can mount different nand brand type. Try to use the full scan
detection and not the onfi one

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>