Fixes for TZC configuration on FVP

The TZC configuration on FVP was incorrectly allowing both secure
and non-secure accesses to the DRAM, which can cause aliasing
problems for software. It was also not enabling virtio access on
some models.

This patch fixes both of those issues. The patch also enabless
non-secure access to the DDR RAM for all devices with defined IDs.

The third region of DDR RAM has been removed from the configuration
as this is not used in any of the FVP models.

Fixes ARM-software/tf-issues#150
Fixes ARM-software/tf-issues#151

Change-Id: I60ad5daaf55e14f178affb8afd95d17e7537abd7