nitrogen6x: Migrate DDR_MB to Kconfig

Move the CONFIG_DDR_MB symbol to Kconfig.  A later clean-up would be to
make dynamic memory size detection work based on how this is done on
other i.MX6 platforms.

Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Troy Kisky <troy.kisky@boundarydevices.com>
10 files changed