The TSP's linker script used to assume that the TSP would
execute from secure DRAM. Although it is currently the case
on FVPs, platforms are free to use any secure memory they wish.

This patch introduces the flexibility to load the TSP into any
secure memory. The platform code gets to specify the extents of
this memory in the platform header file, as well as the BL3-2 image
limit address. The latter definition allows to check in a generic way
that the BL3-2 image fits in its bounds.

Change-Id: I9450f2d8b32d74bd00b6ce57a0a1542716ab449c