m28evk: add trimffs to nand command

this is usefull when writing an UBI image which contains
and UBIFS volume (check README.nand and UBI FAQ for more
details)
Signed-off-by: NMarek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>

include/configs/m28evk.h

@@ -70,6 +70,7 @@
 #define CONFIG_CMD_MII
 #define CONFIG_CMD_MMC
 #define CONFIG_CMD_NAND
+#define CONFIG_CMD_NAND_TRIMFFS
 #define CONFIG_CMD_NET
 #define CONFIG_CMD_NFS
 #define CONFIG_CMD_PING