LOAD_IMAGE_V1: Align BL2 memory layout struct to 8 bytes

In LOAD_IMAGE_V1 (i.e when LOAD_IMAGE_V2=0) the bl2_tzram_layout is,
by default, assigned to the bl1_tzram_layout->free_base which is
dynamically calculated based on the images loaded in memory. There is a
chance that the bl2_tzram_layout will be assigned a value not aligned to
8 bytes. This patch rounds up the free_base value for the required
alignment.

This doesn't happen in LOAD_IMAGE_V2 because the bl2_tzram_layout is
assigned by default to the bl1_tzram_layout->total_base, which is
aligned.

Change-Id: Idc583e7dad993d02ac6791797406118c96f83fa1
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>