bl2-el3: Fix bl32 lr_svc used for bl33 entry address ...

When using BL2_EL3, we need to ensure that lr_svc is
properly given to bl32 as it was previously made by bl1.

Fixes ARM-Software/tf-issues#562

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>

bl2-el3: Add BL2_EL3 image ...

This patch enables BL2 to execute at the highest exception level
without any dependancy on TF BL1. This enables platforms which already
have a non-TF Boot ROM to directly load and execute BL2 and subsequent BL
stages without need for BL1.  This is not currently possible because
BL2 executes at S-EL1 and cannot jump straight to EL3.

Change-Id: Ief1efca4598560b1b8c8e61fbe26d1f44e929d69
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>