board/bsh/imx8mn-bsh-smm-s2: erase the entire NAND chip

If an attempt is made to create a UBI volume and it already exists, the
operation fails. Therefore, before requesting the creation of a UBI
volume, we erase the entire NAND to ensure that no errors occur.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 97ac89eb115dbcd28efd1cf95d9a308f71b33041)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

board/bsh/imx8mn-bsh-smm-s2/nand-full.lst

@@ -10,6 +10,8 @@ SDPS: boot -f _flash.bin
 
 FB: ucmd setenv fastboot_buffer ${loadaddr}
 FB: download -f _image
+FB[-t 10000]: ucmd nand erase.chip
+
 # Burn image to nandfit partition if needed
 FB: ucmd if env exists nandfit_part; then nand erase.part nandfit; nand write ${fastboot_buffer} nandfit ${filesize}; else true; fi;
 FB: ucmd nandbcb init ${fastboot_buffer} nandboot ${filesize}