FVP: map non-secure DRAM1 in the MMU

FVP: map non-secure DRAM1 in the MMU

This patch maps the non-secure region of DRAM1 in the MMU. The
non-secure region comprises the whole DRAM1 (0x80000000 -
0xffffffff) excluding the top 16 MB (0xff000000 - 0xffffffff).
The TrustZone controller configures this 16 MB region as secure
memory, so it can not be accessed in non-secure mode.

The number of MMU tables in BL2 has been increased to 3 because
the new size of the non-secure region in DRAM requires an extra L2
table.

Change-Id: I5ad080c6e181f6b6060e15cebb1d18b7fa128cf5