Recent versions of the i.MX8MQ ATF (like the one shipped with Barebox)
reside in a part of OCRAM, so there is no need to reserve any part of
SDRAM anymore.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>