configs: imx8mn_bsh_smm_s2: add mtdparts to bootargs

Passing the mtdparts environment variable to the Linux kernel is
required to properly mount the UBI rootfs.

Co-developed-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
diff --git a/include/configs/imx8mn_bsh_smm_s2.h b/include/configs/imx8mn_bsh_smm_s2.h
index 1eff8c4..d09c2ab 100644
--- a/include/configs/imx8mn_bsh_smm_s2.h
+++ b/include/configs/imx8mn_bsh_smm_s2.h
@@ -18,6 +18,7 @@
 	"mtdparts=" CONFIG_MTDPARTS_DEFAULT "\0" \
 	"nandargs=setenv bootargs " \
 		"${optargs} " \
+		"mtdparts=${mtdparts} " \
 		"root=${nandroot} " \
 		"rootfstype=${nandrootfstype}\0" \
 	"nandroot=ubi0:root rw ubi.mtd=nandrootfs\0" \