We are running with the caches disabled when mctl_mem_matches gets called,
but the cpu's write buffer is still there and can still get in the way,
add a memory barrier to fix this.
This avoids mctl_mem_matches always returning false in some cases, which
was resulting in:
U-Boot SPL 2015.07 (Apr 14 2016 - 18:47:26)
DRAM: 1024 MiB
U-Boot 2015.07 (Apr 14 2016 - 18:47:26 +0200) Allwinner Technology
CPU: Allwinner A23 (SUN8I)
DRAM: 512 MiB
Where 512 MiB is the right amount, but the DRAM controller would be
initialized for 1024 MiB.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
bfb33f0bc4