Simplify entry point information generation code on FVP

This patch reworks FVP specific code responsible for determining
the entry point information for BL3-2 and BL3-3 stages when BL3-1
is configured as the reset handler.

Change-Id: Ia661ff0a6a44c7aabb0b6c1684b2e8d3642d11ec
Merge pull request #151 from vikramkanigiri/vk/t133-code-readability

Simplify entry point information generation code on FVP