If the SDRAM is not cleanly shutdown before reset it can be left driving
the bus, which then stops the bootloader booting from NAND.
Signed-off-by: Peter Horton <phorton@bitbox.co.uk>
[nicolas.ferre@atmel.com: change file header line order]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>