of: fix reserved memory handling

of: fix reserved memory handling

Mainline u-boot marks some secure monitor relate memory with the
/memreserve/ device-tree method. On the other hand, the same memory is
already defined in /reserved-memory node with the all details needed to
use it by the respective secure monitor deamon. Check for such case and
properly initialize such reserved memory regions instead of returning a
failure.

This allows to use vendor kernel with mainline u-boot on Amlogic SoCs.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: I0bd3b51899cc17f17d1bcbd0c2c5a0d88686b245