OP-TEE may have extra images to be loaded. Load them one by one and do
the parsing. In this patch, ARM TF need to load up to 3 images for
OP-TEE: header, pager and pages images. Header image is the info about
optee os and images. Pager image include pager code and data.  Paged
image include the paging parts using virtual memory.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>