TI: DaVinci DM365: Minor config cleanup

The DM365 config was using the 'CONFIG_CMD_SAVEENV' flag.
This is already included when we include the
config_cmd_default.h header file. So this flag is removed.
Also another flag to enable NAND functions was being
enabled incorrectly.

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>