ARM: dts: tegra: Increase prefetchable PCI memory space

Instead of evenly splitting the 512 MiB area between prefetchable and
non-prefetchable memory spaces, increase the prefetchable memory space
to 384 MiB while at the same time decreasing the non-prefetchable memory
space to 128 MiB. This is a more useful default as most PCIe devices
require more prefetchable than non-prefetchable memory.

Signed-off-by: Jay Agarwal <jagarwal@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>