Remove NSRAM from FVP memory map

This memory is not used by the FVP port and requires an additional
4KB translation table.

This patch removes the entry from the memory map and reduces the
number of allocated translation tables.

Fixes ARM-software/tf-issues#196

Change-Id: I5b959e4fe92f5f892ed127c40dbe6c85eed3ed72
Merge pull request #143 from athoelke/at/remove-nsram

Remove NSRAM from FVP memory map